Two-dimensional gradients in magnetic properties created with direct-write laser annealing

Domain: physics
Published: 2025-12-09
Editorial outcome: minor_revision

Abstract
Acrossthefieldsofmagnetism,microelectronics,optics,andothers,engineeredlocalvariationsinmaterialpropertiescanyieldgroundbreakingfunctionalitiesthatplayacrucialroleinenablingfuturetechnologies.One-dimensionallateralgradientsinmaterialpropertiesgiverisetoaplethoraofneweffectsinthin-filmmagneticsystems.However,extendingsuchgradient-inducedbehaviorstotwodimensionshasbeenchallengingtorealizeexperimentally.Here,wedemonstratethecreationoftwo-dimensionalcomplexpatternswithcontinuousvariationsinmagneticanisotropy,interlayerexchangecoupling,andferrimagneticcompensationatthemesoscopicscaleinnumerousapplication-relevantmagneticmaterials.Weexploitourengineeredgradientsinmaterialpropertiestodemonstratenovelmagneticfunctionalities,includingthecreationofaspinwavebandpassfilterandanarchitectureforpassivelyresettingthepositionofamagneticdomainwall.Ourresultshighlighttheexcitingnewphysicsanddeviceapplicationsenabledbytwo-dimensionalgradientsinthinfilmproperties.

Introduction
Overthepastfewyears,therehasbeenanintenseresearchendeavor tocreateandunderstandtheuniqueeffectsandfunctionalitiesthat emergewhenmaterialpropertiesarevariedinagradientmannerover micro-andnanoscalelateraldimensions1–10.Withinthefieldofmagnetism,thetechnologicalnecessityofengineeringcomplexmagnetic energy landscapes has been demonstrated by recent reports on a number of novel, one-dimensional(1D) gradient-induced effects11–16. Forexample,ithasbeenshownthatthesymmetrybreakingoriginatingfromlateralgradientsinthemagneticcompensationtemperature of ferrimagnets11 or from varying the magnitude of the interlayer coupling strength of synthetic antiferromagnets12 enables magnetic field-free switching of magnetic elements using spin-orbit torques. As all-electrical control of magnetization is necessary to realize energy-efficient,high-densityspintroniccomputingarchitecturessuch asmagneticrandom-accessmemory(MRAM),thereisacrucialneedto develop scalable techniques to enact these functionalities17–19. In addition,movingbeyond1Dtocomplexmultidimensionaldesignscan yieldnoveldevicesandnewphysics.

Gradientsinmagneticpropertiesarealsoparticularlyrelevantto unconventional, beyond-von Neumann computing schemes. For instance, localized gradient changes in the anisotropy strength of ferromagnetic materials can impact both the propagation direction anddispersionofmagnons20,21,aswellasthedynamicsofmagnetic domainwalls(DWs)astheymovethroughthegradient22.Indeed,ithas longbeenpredictedthatsufficientlystronggradientsinperpendicular magneticanisotropystrengthshouldenablespontaneous,self-driven DWmotion23,whichisrelevantforDW-basedin-memoryandneuromorphiccomputing applications.However,anexperimental realization of the requisite anisotropy energy landscape has remained elusive.

Typically,magneticpropertieshavebeenmodifiedatsmalllength scalesandinintricatepatternsusingfocusedbeamsofions(typically He+ orGa+)andelectrons,aswellasthermalscanningprobes14,24–28. However,theseapproachesgenerallyrequirespecializedequipment and ultra-high vacuum environments.Furthermore, the scanning of focusedionbeamsoverlargeareasistypicallyslowandsuffersfrom dose instability29,30. Because of these challenges, performing systematicstudiesbecomesprohibitivelytime-consuming31,andseveral concernsregardingtheindustrialscalabilityoftheseprocesseshave yettobeaddressed32,33.Assuch,developingnewtechniquestolocally impartgradientsinmagneticpropertiesthatallowforrapiditeration andindustrialscalabilitywoulddramaticallyexpandtheavenuesfor research.

Laser annealing, in which thermal energy is imparted to a materialusingafocusedlaserbeam,hasbeenusedinmagnetism to modify the saturation magnetization, exchange bias, and magnetic easy axis orientation of thin films34–36. However, the instruments used to perform laser annealing have typically been lab-built,bespokesetupsofferinglaserspotsizesontheorderof 10 μm–20 μm without any complex, high-resolution patterning capabilities28.Thus,laserannealinghasnotshownmuchpromise up to now as an applications-relevant technique for micro- or nanoscale devices. More recently, the suitability of direct-write laser annealing (DWLA) for achieving local, binary modifications inmaterialpropertieshasbeendemonstrated37,38.BecauseDWLA can be performed using existing laser-based photolithography equipment and does not require patterned resist layers or ultra-high vacuum environments39, the process is significantly streamlined compared to other approaches, allowing for rapid optimizationofexposureparametersthatyielddesirablematerial changes.However,complex,two-dimensional(2D)gradientsina variety of magnetic properties and materials have yet to be demonstratedusing DWLA.

Here,wedemonstratethecreationofcomplex2Dgradientsinthe materialpropertiesofthinfilms,includingcrystallization,oxidation, andinterdiffusion,byDWLA.Inturn,theselocalchangesareusedto create elaborate magnetic energy landscapes in several important magnetic thin-film systems. In particular, we locally engineer continuous variations in the magnetic anisotropy in ferromagnetic and syntheticantiferromagneticmaterials,thecompensationtemperature of ferrimagnets, and the interlayer exchange coupling strength of syntheticantiferromagnets (SAFs), exemplifying the broad utility of DWLA.Furthermore,wedemonstratethemanipulationofspinwaves andmagneticdomainwallswithmagneticpropertygradients,highlightingtherelevanceof2Dgradientsinmaterialpropertiesformagnonicsandspintronicsresearchandapplications.Theseresultsbring newfunctionalityandrelevancetolaserannealingasatechniqueto engineerdesirablematerialperformance.

Results
In Fig. 1, we summarize the various physical properties that can be modified using DWLA and how they impact magnetic properties. The process of DWLAis depicted within the innermost oval of Fig. 1. The laser is raster scanned in a serpentine path (indicatedbythewhitedashedline)overthesample,withthefluence automaticallyadjustedfollowingwhateverdesignisinput,which here gives a linear gradient in fluence. At each point, the laser deposits thermal energy locally at the sample surface, which is partially absorbed by the film and dissipated through the substrate. The resulting temperature increase occurs ~100 nm into the film (see Supplementary Fig. S1), but we choose thin film heterostructures with a total thickness <20 nm to maximize the uniformityoftemperatureincrease throughthe thicknessofour films. We use Si substrates with a 300 nm-thick SiOx coating because of their low thermal conductivity, which maximizes the temperature increase in the film for a given laser fluence. The larger oval encompasses the material changes we observe in different thin film systems due to DWLA, including crystallization, oxidation, and interdiffusion. Example magnetic configurations resulting from the microstructural changes are shown: gradients in the (i) magnetic anisotropy due to crystallization or interdiffusion,(ii) interlayer exchange coupling dueto interdiffusion, and(iii) magnetic compensation due tooxidation.

ControllingstructuraltransformationswithDWLA
TograsptherangeofapplicationspossiblewithDWLA,itisimportant tounderstandthemicrostructuralchangesenactedindifferentfilms duringtheannealingprocess.Giventhatthe405nm-wavelengthlaser lightweemployiswellbelowthebandgapofsilicon,andallmaterials implementedherearemetallic,thelaseractsasalocalheatsource. Here,weoutlinethethreechangesinphysicalpropertiesobservedby laser annealing films: crystallization, oxidation, and interdiffusion (showninthelargerovalofFig.1).TodemonstratethatDWLAisa broadly applicable technique — both inthe range of physical transformations it induces and wide variety of possible materials — we examineitseffectonthefollowingmaterialsystems:(1)ferromagnetic CoFeB/MgO thin films, (2) ferrimagnetic CoGd films, and synthetic antiferromagnetscomposedof(3)Co/Cr,(4)Co/Taor(5)CoFeB/Pt/Ru (detailsofsamplecompositionsaregivenin“Synthesis”).Thesewere chosen because researchers performing uniform annealing experimentsobservedonedominantphysicaltransformationinthesesystemsinthetemperaturerangeof200°Cto500°C40–44.

The evolution of the microstructure of CoFeB/MgO heterostructuresonheatinghasbeenextensivelyinvestigatedduetotheiruse inmagnetictunneljunctions,whichareubiquitousinMRAMdevices. Here, it is known that thermal annealing induces crystallization of CoFeB/MgO layers45. In Fig. 2a, cross-sectional transmission electron microscopy(TEM)imagesoftwolamellaecutfromasinglesampleare compared,where one lamella is cut from an as-grown region (upper image),andtheotheriscutfromaregionthathasbeenlaserannealed atafluenceof2.5Jcm−2(lowerimage).TheCoFeB/MgOlayersintheas-grown sample are hard to distinguish from one another, and no diffraction peaks in the accompanying electron diffraction patterns are noticeable. For the lamellafrom the laser annealed region,there is a significant contrast difference between the two layers, suggesting a differenceindensity.Inaddition,diffractionpeaksbecomevisiblefor theselayers,similartotheappearanceofdiffractionpeaksobservedin ultrathin CoFeB/MgO annealed in a furnace40. Complementary x-ray reflectivity(SupplementaryFig.S2)andmagnetometrymeasurements (Supplementary Fig. S3) suggest minimal interdiffusion or oxidation. Fromthis,wecanconcludethattheCoFeB/MgOhascrystallizedasa resultofDWLA(TEMmicrographsoflargerregionsofeachlamellaare showninSupplementaryFig.S4).WhilelaserannealingofCoFeB/MgO hasbeenpreviouslydemonstrated46,wehavethenewabilitytotunethe degreeofcrystallizationlocally.

Next, we consider the ability of DWLA to modify the chemical compositionofthinfilms.TheoxidationofferrimagneticCoGdfilmsin responsetoDWLAwasevaluatedusingdynamicsecondaryionmass spectroscopy (SIMS). For this,anAr+ ion beamisused to gradually remove the film, layer by layer, by sputtering. The secondary ions producedduringsputteringareelectrostaticallyguidedtoaquadrupoledetector,whichfiltersionsbasedontheirmassandcharge.Inour case,theinstrumentwastunedtoselecttoO−ions.Comparingthe SIMSprofilesofanas-grownCoGdfilmwithaCoGdfilmafterexposure withalaserfluenceof2Jcm−2(seeFig.2b),itbecomesevidentthat laserannealingsignificantlyincreasestheoxygencontentwithinthe CoGdlayer.ThechemicalchangesweobserveinresponsetoDWLAin ourCoGdferrimagnetsareinagreementwithpreviousworkinwhich the oxygen content of ferrimagnetic films was modified using an oxygenplasma,ionirradiation,orfurnaceannealing41,47,48.Thischange in the oxygen content in response to DWLA occurs without significantly modifying the crystal structure of the CoGd system (see SupplementaryFig.S5).

Thefinalphysicaltransformationweobserveinthinfilmsafter laser annealing is interdiffusion, which we detect in synthetic antiferromagnets through x-ray diffraction following the method given in ref. 43. A symmetric 2θ − ω scan of a CoFeB/Pt-based synthetic antiferromagnetwithaRuinterlayerinthe2θrangewherefilmpeaks appear (blue curve in Fig. 2c) reveals one primary diffraction peak for as-grown films corresponding to Pt (111), as well as two small peaks corresponding to two different Ta phases. Half of the film is laserannealedatafluenceof3.6Jcm−2,anditcanbeseenthatthis halfofthefilmhasadifferentprimarypeakata2θvaluehigherthan thatoftheas-grownregion(redcurveinFig.2c).Thisnewpeaklocation corresponds to the (10 (cid:1) 1) diffraction peak of several CoPt and FePt alloys. None of the peak locations match alloys with Ru (see Supplementary Fig. S6 for the XRD scan over a broad 2θ range). WeexcludeoxidationintheseheterostructuresthroughSQUID-VSM measurements of the magnetization before and after annealing (see Supplementary Fig. S7). In addition, using a combination of x-ray diffraction measurements, SIMS measurements, and comparisons to films deliberately alloyed during growth, we find that the Co/Cr/Co- and Co/Ta/Co-based heterostructures also experience interdiffusioninresponsetolaserannealingwithoutachangeintheir crystalline structure (see Supplementary Fig. S8). Altogether, these resultsdemonstratethatourDWLAapproachcangiveinterdiffusionin thin metallic layers that is also seen with furnace annealing or ion irradiation42,49.

Inthefollowingsections,weimplementDWLAinmagneticthin filmsystemstocreategradientsinmagneticpropertiesformagnonics andspintronicsapplications.However,thesephysicalchangesarenot limitedtomagneticfilmsandcanbeimplementedintoanythinfilm materialthatundergoesathemally-inducedstructuraland/orchemical change. For example, phononic and photonic metamaterials havebeenmadebynanostructuringmaterials50,butcreatinggradients intherefractiveindexofamaterialcouldwidenpossibilities.Indeed, veryrecently,DWLAwasusedtocreatephotoniccircuitsbymodifying thecrystalstructureofathinfilminabinarymanner38.Ourgradient techniquethereforedramaticallyexpandsthepossibilitiesforphotonic devices. In addition, while surface roughness gradients created usingmultiplechemicalandmicrofluidicpatterningstepshavebeen usedtocontrolthepropertiesofculturedcells51,DWLAoffersapathto obtain similar effects through a substantially more straightforward fabricationprocess.

TuningmagneticpropertieswithDWLA
Having demonstrated that DWLA enables a variety of physical and chemical changes in thin film systems, we now link these physical changestochangesinthemagneticproperties.Tocharacterizethe ways in which DWLA affects the magnetic properties of different materials systems, we measure areas annealed with different laser fluences across a single film (see “Magneto-optic Kerr effect measurements“ and “Magnetic characterization” for more details). This allows us to record small changes in magnetic properties due to increased laser fluence without having to account for variations in growthconditions,andthereforethemagneticproperties,thatoften existbetweensamplesgrownatdifferenttimes.

In the case of CoGd transition metal-rare earth ferrimagnets, wefindthattheoxidationfacilitatedbyDWLA,showninFig.2b,provides a means to tune the dominant magnetic sublattice at a given temperature (i.e., whether the Co magnetization aligns antiparallelorparalleltotheappliedmagneticfield).Forlaserfluences <1.3 J cm−2, the coercivity at room temperature increases with increasingfluence,whileforfluences>1.3Jcm−2,thecoercivitydecays withincreasingfluence(Fig.3a).FrompolarMOKE(pMOKE)hysteresis loops (see Supplementary Fig. S9a), we observe that perpendicular magnetic anisotropy is maintained over the range of laser fluences usedascanbeseenfromtheconsistentsquarenessofthehysteresis loops. Furthermore, we find that the sign of the Kerr rotation measuredinourhysteresisloopschangesfrompositivetonegative asthelaserfluenceisincreasedacrossthepointwherethecoercivity diverges (shown for laser fluences of 0.8 J cm−2 and 1.6 J cm−2 inFig.3aandforallfluencesinSupplementaryFig.S9a).Giventhe configurationofourMOKEmicroscopyplatform(see“Magneto-optic Kerr effect measurements“ for details), this indicates that laser annealing changes the magnetically dominant sublattice. The divergenceinthecoercivityandthechangeinthesignoftheKerrrotation showninFig. 3a arecharacteristicofferrimagnets in the vicinityof achangeinthedominantmagneticsublattice.Thiscanbetheresult of a change in thickness, temperature, proportion of TM to RE atoms, ion irradiation dosage, or, as in our case, oxidation44,47,52–54. The change in the degree of ferrimagnetic compensation revealed byourMOKEcharacterizationisfurtherconfirmedbymagnetometry measurements of continuous films uniformly exposed using various laser fluences (see Supplementary Figs. S9b and S9c). Here we observe a net magnetization of zero in the vicinity of the fluencewherethecoercivitydivergesinFig.3a(~1.3Jcm−2),indicating thatthemagnetizationoftheCoandGdsublatticesisofequalmagnitude and opposite orientation, as expected at ferrimagnetic compensation.

WenowturntoCoFeB/MgO-basedheterostructures,wherecrystallizationoftheCoFeB/MgOlayersduetolaserannealing,showninFig.2a, canyieldstrongperpendicularmagneticanisotropy(PMA)resultingfrom hybridizationoftheFe-Oorbitals.Todemonstratethischangeinanisotropy, CoFeB/MgO films are grown with in-plane magnetic anisotropy. Asareasofthefilmarelaserannealedwithincreasingfluence,theeffective magnetic anisotropy field μ H , extracted using planar and 0 K,eff anomalous Hall effect measurements, decreases (Fig. 3b), indicating a decrease in in-plane anisotropy (see “Magnetic characterization” for detailsconcerningtheextractionofμ H ).Atafluenceof2.45Jcm−2, 0 K,eff μ H becomesnegative,correspondingtoachangeofthemagnetic 0 K,eff easyaxisfromin-planetoout-of-plane.Whenthelaserfluenceisincreased above3.15Jcm−2,μ H becomespositiveagain,returningtoin-plane 0 K,eff magneticanisotropy.Theseresultsareconsistentwiththoseobtainedby furnaceannealingCoFeBfilms,wherethereisanoptimaltemperature rangeof ~200°C–350°CthatpromotesstrongPMA45.Weconfirmthat laserannealingandfurnaceannealinggivesimilareffectsbycomparing films subjected to each treatment (see magnetic hysteresis loops in SupplementaryFig.S10).However,laserannealingprovideslocalcontrol impossible to achieve with furnace annealing. Rather than a uniform transformation of properties, an anisotropy energy range of up to ΔK ≈3×105Jm–3canbecreatedinarbitrarymicroscalepatternsinthe eff filmplane.

Now,weshowhowthelaserannealing-inducedinterfacialinterdiffusion of Co/Cr/Co SAFs modifies the interlayer exchange, or Ruderman-Kittel-Kasuya-Yosida (RKKY), coupling strength. To demonstratehowtheuniquetwo-dimensionalpatterningwithDWLA allowsforthecreationofdramaticgradientsinmagneticproperties withinsmallareas,weconsidertheimpactofaspiral-shapedfluence gradient applied to a magnetic structure, as shown in the inset of Fig. 3c. The as-deposited Co/Cr/Co SAF sample exhibits a pMOKE hysteresislooptypicalofSAFswithPMA(seeSupplementaryFig.S11a). FromthispMOKEhysteresisloop,wecandefinetheRKKYcoupling fieldμ H ,whichreflectstheRKKYcouplingstrength,asthemag- 0 RKKY netic field about which the fields associated with the two spin-flip transitionsbetweenantiparallelandparallelalignmentarecentered. Theas-grownsamplepossessesaμ H of360mT.FrompMOKE 0 RKKY hysteresisloopsrecordedfromareasalongthespiralstructuresubjectedtolaserfluencesintherange0Jcm−2to4.5Jcm−2,wefindthat thereisadecreaseinμ H asafunctionoflaserfluence,asshownin 0 RKKY Fig. 3c (see Supplementary Fig. S11a for pMOKE loops at these fluences).Atafluenceofapproximately4Jcm−2,aspin-fliptransitionisno longerapparentinthepMOKEhysteresisloops(seeSupplementary Fig.S11a),suggestingthatthetwoFMlayerscomprisingtheCo/Cr/Co SAF structure are no longer antiferromagnetically coupled to each other,towhichweassignaμ H valueofzero.Webelievethisis 0 RKKY duetotheCrspacerlayerbecomingmagneticbyinterdiffusion(see SupplementaryFig.S8),transformingtheCo/Cr/CoSAFstructureto that of a ferromagnetic heterostructure55,56. This ability to tune the RKKY coupling strength is achieved while leaving the saturation magnetization relatively unchanged (see Supplementary Fig. S11b). Thisindicatesthateachferromagneticlayerhasmagneticproperties similartothoseofthelayersoftheas-grownfilm,andthechangeininterlayer exchangecouplingis due toachange in thespacerlayer properties.

Finally, by implementing different materials in a SAF heterostructure, namely CoFeB/Pt/Ru, interdiffusion with DWLA can be leveragedtomodifythemagneticanisotropyoftheSAFwhileleaving theRKKYcouplingunchanged.TwoCoFeB/Ptmagneticmultilayers separatedbyaRuspaceraresynthesizedforthispurpose.Ithasbeen foundthatPMAislostinCoFeB/Ptmultilayerswhenthestructureis annealed above ~300°C43 due to interdiffusion that disrupts the interfacial anisotropy. Ru spacer layers are typically stable up to ~400 °C57, so there is a process window where the CoFeB/Pt is affected, but the Ru is not. Interdiffusion indicated by XRD measurements given in Fig. 2c suggests that laser annealing should produce a similar decrease in PMA. Indeed, as the laser fluence is increasedfrom2.6Jcm−2to3.9Jcm−2,weobserveachangeinthe shapeofthepMOKEloopfromthatofaspin-flipSAF,where thereis sharpswitchingcenteredatμ H ,tothatofaspin-flopSAF,where 0 RKKY switching from antiferromagnetic to ferromagnetic alignment occurs gradually, reflecting weaker PMA (see Fig. 3d). Despite the change in shape of the pMOKE loop, μ H does not change 0 RKKY withlaserfluence.Weconcludethattheinterdiffusionwithineach magnetic layer leads to a change in magnetic anisotropy of the CoFeB/Pt/RuSAFasthelaserfluenceincreases–fromstronglyout-of-plane,toweaklyout-of-plane,toin-plane,withoutdisruptingthe RKKYcoupling.Thisisconfirmedwithmagnetometrymeasurements (seeSupplementaryFig.S7).

Large-areatunableanisotropygradientsformagnonics
To demonstrate the utility of 2D gradients in magnetic properties formagnonicsapplications,alarge-areagradedindexdesignisfabricated in CoFeB/MgO films. For this, a 3 mm × 3 mm area is laser annealedwithrepeating3μm-widelineargradientstripes,asshownin Fig.4a.Thelaser fluence range ischosensuch thatK variesfrom eff 4.4×105Jm−3to6.2×105Jm−3(correspondingtoachangeinanisotropyfieldofμ H =0.21Ttoμ H =-0.15T)acrossthestripes. 0 K,eff 0 K,eff Thespinwavedispersion,relatingthespinwavewavelength(givenby 2π/k)tothefrequencyfforagivenappliedmagneticfield,ismeasured withwavevector-resolvedBrillouinlightscattering(BLS)spectroscopy and simulated with mumax358,59 (simulation details can be found in SectionS4.1andSupplementaryFig.S12oftheSupplementaryInformation).WecharacterizetheDamon-Eshbachmode,wherethespin waves propagateperpendiculartotheapplied magnetic field(schematically shown in Fig. 4a). The wavevector-resolved BLS measurementdoesnothavespatialresolution,sothesignaliscollectedfroma 30μmlaserspot,coveringmultiplerepetitionsofgradientstripes. The resulting dispersion at three fields is shown for simulations in Fig.4bandforBLSmeasurementsinFig.4c.

The as-grown film has a single spin wave mode, shown by thedashedwhitelinesforthethreedifferentappliedmagneticfields in Fig. 4b. After creating the graded stripe pattern with DWLA, a broadplateauofintensityfrom6GHzto9.5GHzismeasuredwithBLS atμ H=0.22T,seeninthetoppanelofFig.4c.Thissuggeststhatthese 0 graded anisotropy stripes act as a band pass filter for spin waves, allowingonlyspinwavesina3.5GHzrangetopropagate,andthese frequenciescanbetunedwiththeappliedmagneticfieldto7.3GHz– 10.8GHzatμ H=0.26Tand9.8GHz–13.3GHzatμ H=0.35T,seenin 0 0 the middle and lower panels of Fig. 4c, respectively. Furthermore, micromagneticsimulations(Fig.4b)reproducetheBLSdatawithhigh fidelity (see Supplementary Fig. S13 for a comparison at specific wavevectors), reflecting the ability to precisely fabricate a desired magnetic anisotropylandscape in films.Toverifythatthe designed gradientpatternintheanisotropywasaccuratelyreproducedinthe film,wehavealsocomparedsimulationandBLSdataforspinwave propagation orthogonal to the gradient stripes in Supplementary Fig.S14.Ifanarrowerfilterisdesired(1.5GHzbandwidth,forexample), this canbe constructed by writing shallower gradients (see SupplementaryFig.S15).

Todate,gradientmagnonicdeviceshavebeenmadewithion irradiation, which can damage films and increase magnetic dampingathigherdoses16.Withlaserannealing,thefilmqualityis maintained, and can even be improved (for example, the emergent crystallinity seen by comparing the TEM images in Fig. 2a). Fortheimplementationofgradedmagnoniccrystalsindevices,it is necessary for spin waves to interact with changes in magnetic properties without increased dissipation, given by the Gilbert damping parameter. By measuring the ferromagnetic resonance linewidth μ ΔH at a number of excitation frequencies 0 FMR (Fig.4d),weobtainamagneticGilbertdampingfortheas-grown film of α = 0.018 ± 0.002, while for a uniformly annealed film, α = 0.020 ± 0.002 (see “Magnetic characterization”). This consistent damping despite a change of magnetic anisotropy (μ ΔH = 0.1 T) makes DWLA promising for applications in 0 K,eff magnonics,wheremaintaininglowdampingisessentialforhigh-performancedevices.

2Danisotropygradientsforspintronics
Themanipulationofmagneticdomainwallswithelectriccurrentsis important for next-generation in-memory computing. For example, recentcomputationalworkhasshownhowthespontaneousmotionof domainwallsinresponsetoagradientinanisotropyenergycanbe implementedasanartificialneuron60.SAFsareparticularlywell-suited forthispurpose,asantiferromagneticsystemsarepredictedtohave high spontaneous domain wall velocities23, enabling observation of spontaneousdomainwallmotionontheμmscaleinthetimespanof severalseconds.Here,weconstructa2Dgradientinmagneticanisotropyinasyntheticantiferromagnet,creatingadevicethathasbeen theoreticallyproposed23,buthasnotbeen realizeddue toalackof appropriate nanofabrication methods. We experimentally demonstrate the predictedspontaneousdomainwallmotionandobserveit overmicrometer-scaledistances.

Wefabricatea3μm-widecirculardomainwalltrackinaCoFeB/Pt/ RuSAFwherethelaserfluencelinearlyincreasesalongthetrack(see Fig.5a).Itisnotpossibletofabricatesuchastructurewithmostother methodsexceptionirradiation,whichsuffersfromdifficultyinmaintainingconstantdosesradially22.Thelinearincreaseinlaserfluence leadstoalineardecreaseinthePMAoftheCoFeB/Pt/RuSAF,with ΔK =1.5×105Jm–3alongthe72μmaveragecircumferenceofthe eff circle(seehard-axishysteresisloopsinSupplementaryFig.S7b).The bottommagneticlayeroftheSAFstructurehasalargermagnetization thanthetoplayersothattheKerrcontrastobservedcorrespondsto themagneticstateofthelowermagneticlayer.Thedeviceisinitialized witha-30mTout-of-planemagneticfieldtoadown-upstate,referring tothemagnetizationdirectioninthebottomandtopmagneticlayer, respectively.Whena+4.5mTmagneticfieldisapplied,anup-down domain (dark contrast in Fig. 5b) nucleatesinthelowestanisotropy area(indicatedbythewhitedumbbellinFig.5b–e),andonedomain wall(DW1)propagatescounterclockwisealongthecircularanisotropy gradient (Fig. 5c). Due to the anisotropy energy barrier, the other domain wall(DW2) isprevented from moving clockwise, as seen in Fig.5b,c.Whenthefieldisremoved,DW1retreatstotheareawiththe lowestanisotropy, moving spontaneously downthe anisotropy gradientatanaveragespeedof ~580nms−1(basedonthetotaldistance traveledbythedomainwallintheobserved86s),asseeninFig.5d,e.

Sucharesettingfunctionalitycanfulfilloneofthecrucialcriteriaforan artificial neuron in neuromorphic computing devices. Furthermore, these curved gradient tracks can be implemented as a feedback mechanismfordomainwalllogic,sotheoutputofalogicgatecanbe fed back into an input. This is essential for the development of in-memorycomputing61.

Methods
Synthesis
AllfilmsweredepositedonSisubstrateswitha300nm-thickthermal oxidecoating(referredtoasSiOx)usingmagnetronsputteringina 0.4PaArpartialpressure.Forthis,weusedanATCOrionsputtering tool(AJAInternational,Inc.),whichhadabasepressureof2×10−6Pa. MgOandTaweredepositedwithRFsputtering,whileallotherlayers weredepositedwithDCsputtering.Thefullcompositionsofthefilms aredetailedbelowfromthelowestlayernexttothesubstratetothe uppermostlayerineachstack,whereallthicknessesareinnm:
• CoFeB/MgO ferromagnetic films, with the structure Ta(5)/ Co Fe B (1.3)/MgO(1.5)/Ta(5) were sputtered at powers of 40 40 20 80WforTa,40WforCoFeB,and150WforMgO.
• CoGd ferrimagnetic films with the structure Ta(2)/Pt(5)/ Co Gd (5.5)/Ta(3)weredepositedusingaco-sputteringtechni- 70 30 que, in which the Co, Gd, Ta, and Pt were deposited using sputteringpowersof50W,24W,100W,and100W,respectively. The subscripts used to specify the stoichiometry of the CoGd layercorrespondtoatomicpercentages.
• The Co/X/Co (X = Cr or Ta) SAFs have the composition Ta(2)/ Pt(3)/Co(0.7)/X/[Co(0.7)/Pt(1)] /Pt(5), with X being Cr(1) or 3 Ta(1.25). All layers were deposited using a sputtering power of100W.
• The CoFeB/Pt/Ru SAFs have the structure Ta(5)/[Pt(1.5)/ Co Fe B (0.4)]/Ru(1.1)/[Co Fe B (0.4)/Pt(1.5)].TaandRu 40 40 20 3 40 40 2 weredepositedatapowerof80W,CoFeBwasdepositedat40W, andPtwasdepositedat100W.
AftertreatmentwithDWLA,theCo/Cr/CoSAFfilmwaspatterned intoa2μm-widespiralfeature(asshowninFig.3c)usingstandardUV photolithographyandionbeametchingtechniques.

Direct-writelaserannealing
A Heidelberg DWL66+ direct-write photolithography system with 405nmwavelengthcontinuouswave(CW)illuminationwasusedto performDWLA(schematicshowninSupplementaryFig.S17a).Inthe “AdvancedGrayscale”configuration,thisplatformprovides256levels of grayscale exposure intensity, which allows for quasi-continuous variationsinlaserfluences.DesignfilesmadeusingcommercialCAD programsmodulatethepowerofthelaserasitisraster-scannedover thefilm.The“Hi-Res”writeheadusedthroughoutthisworkoffersa 50nmaddressgridwithaminimumfeaturesizeof180nm(seeSupplementaryFig.S17b).Themaximumlaserfluencepossibleis ~31Jcm−2. Basedonthepublishedwritespeedof3mm2/minute,weestimatethat eachpixelintheaddressgridisexposedtothelaserfor50nsforany exposure.

Frompreviousreportsonfurnaceannealingwork,weknowthat thedifferentheat-inducedphysicalchangesobservedinourmaterials (crystallization,interdiffusion,andoxidation)occuratdifferenttemperatures.Forexample,theelectronicstructureofrare-earthelements givesGdastrongaffinityforoxidation65,andthustheeffectsofoxidationareobservedafterfurnaceannealingfilmsattemperaturesas lowas100°C44.Assuch,whendesigningapropertygradientinfunctionalthinfilms,onemustconsidertheenergybarrierforaparticular physicalorchemicaltransformation,whichwillinturndefinethelaser fluences needed to obtain the desired changes in the magnetic properties.

Thethicknessofafilmandthesubstrateonwhichitisgrowncan dramaticallyimpactthe temperaturechange in response to a given laserfluenceand the volume within thefilmthatexperiencesa significanttemperaturechange.Fromoursimulationsofheatingdueto laser annealing (see Supplementary Fig. S1), we can conclude the following:
(i) Forthesamelaserexposureparameters,theaveragetemperatureincreaseofametallicfilmisinverselyproportionaltothe thermalconductivityofthesubstrateused.
(ii) Thelateralregionofelevatedtemperatureextendsoveralarger areawhenthemetallicfilmisonasubstratewithhighthermal conductivity.
(iii) Thinner metallic films exhibit a more uniform temperature throughtheirthicknessinresponsetolocalizedsurfaceheating.

Furtherdetailsregardingthethermalsimulationscanbefoundin the“Modelingofthermalproperties"subsectionbelowandSupplementaryFig.S1.

A silicon substrate with a 300 nm-thick thermal oxide (SiOx) coatingwasusedforallexperiments,asthelowthermalconductivity of SiOx (1.3W m−1 K−1) reduces the laser fluence required to obtain significant temperature increases and gives a better localization of the heat to the laser spot position (see Supplementary Fig. S1). Additionally,wenotethatthemaximumfluenceof ~31Jcm−2offered by the DWL66+ makes DWLA suitable for patterning the physical and magnetic properties of films on substrates with higher thermal conductivity,loweropticalabsorptivity,andlowerabsorptionoflaser lightthanthatofsiliconsubstrates,andfortargetingphysicaltransformationswithhighactivationenergies.

Magneto-opticKerreffectmeasurements
Because the magnetic property changes in response to annealing manifestthemselvesintheout-of-planemagneticresponseofourfilms, wecollectedhysteresisloopsinthepolarMOKEgeometrytodetermine howthemagneticpropertieschangewithincreasinglaserfluence.The polar magneto-optic Kerr effect (pMOKE) hysteresis loops were obtained using two different systems: A MOKE magnetometer (optimized for high signal-to-noise hysteresis loop measurements) and a MOKEmicroscope(tailoredforimaging).Thetechniqueusedtocollect thedataextractedfromthehysteresisloopmeasurementsisstatedin thefigurecaptions.Formorecomplexmagneticpatternsinducedby DWLA, the collection of location-specific hysteresis loops was easier usingtheMOKEmicroscope,whereidentifyingtheregionofinterestis morestraightforward,althoughthesignal-to-noiseratioispoorerthan thatoftheMOKEmagnetometer.Similarly,dependingonthephysical transformationinducedbyDWLA,theassociatedchangeintheoptical reflectivityofamaterialcanbesubtle,makingiteasiertodiscernusinga MOKEmicroscopeoptimizedforimaging.

The MOKE magnetometer employed was a NanoMOKE systemmanufacturedbyDurhamMagnetoOptics,Ltdwith660nm wavelengthlaserillumination.AMOKEmicroscopyplatformfrom EvicoMagneticsGmbHfeaturingwide-spectrumLEDillumination was used for imaging. Each system allows for the collection of location-specific hysteresis loops from areas that were annealed using the fluences indicated in the figures. For the ferrimagnets andCoFeB/Pt-basedSAFs,aseriesof50μm ×50μmboxes(with ~200μm spacing between boxes) was annealed with different laser fluences. The spiral structure shown in Fig. 3c, with a laser fluence gradient along the spiral, was used to characterize magnetic changesofthe Co/Cr/CoSAF.

When collecting images of domain states using MOKE microscopy, the contrast of the captured images was enhanced using a background subtraction procedure in which an image collected on application of a saturating magnetic field was subtracted from the recordedimage,asiscommoninMOKEmicroscopy.Thesettingofthe analyzingpolarizeroftheMOKEmicroscopewasadjustedtomaximize the extinction of reflected light with the same polarization as the incidentlight,andsuchthatdark(light)contrastcorrespondstoup (down) magnetization. The pMOKE hysteresis loops for the ferrimagnetswereobtainedwiththesameanalyzingpolarizersetting.The wavelengthofilluminationuseddictatesthatMOKEmeasurementsof ourCoGdferrimagnetswereprimarilysensitivetothemagnetization oftheCosublattice66,67.Toobtain the MOKEmicroscopeimagesin Fig. 5, a Gaussian blur was applied to the original images, and the contrastwasenhanced.UnalteredimagesareshowninSupplementary Fig.S16.

The error of grayscale intensity values for hysteresis loops recordedwithMOKEmicroscopywasdeterminedbycalculatingthe standarddeviationofallnormalizedgrayscalevaluesabovethesample’ssaturationfield(atleast10points)duringeachmeasurement.The uncertainties in the RKKY and coercive field values extracted from MOKE microscopy data are determined by the magnetic field step sizeused.

Structuralcharacterization
X-raydiffractionandreflectivitymeasurementswereconductedusing aBrukerD8Discover,equippedwithamicrofocusedCusource.ANi filterwasusedtopartiallymonochromatetheincidentx-raystotheCu Kα line (0.154 nm). The angular step size Δ2θ for diffraction and reflectivity measurements was 0.03° and 0.02°, respectively. Structuralmodelingofx-rayreflectivitycurveswasperformedusingGenX68 (see Supplementary Fig. S2). The figure of merit for each model was<0.1.

Magneticcharacterization
AQuantumDesignmagneticpropertymeasurementsystem(MPMS) equippedwithsuperconductingquantuminterferencedevice-vibrating sample magnetometry (SQUID-VSM) was used to measure the saturation magnetization of selected continuous films subjected to uniform laser exposure. The standard error of each magnetizationmeasurement,givenbythestandarderrorofallmagneticmomentvalues(atleast26)recordedduringtheacquisitiontime, is<2×10−4Am2,correspondingto<1%errorforeachdatapoint.When extractingthesaturationmagnetizationfromSQUID-VSM,wereport thestandarddeviationofthedatapointsabovethesaturationfieldas themeasurementuncertainty.

EffectiveanisotropyfieldsweredeterminedfromanomalousHall effect(AHE)andplanarHalleffect(PHE)measurementsonaCoFeB filmwithHallbardevicepatterns.ForAHEmeasurements,aDCcurrentisappliedinthexdirection(inthefilmplane),afieldisappliedin thezdirection(outofthesampleplane),andthevoltagealongthey direction isrecorded.μ H isthengivenbythefieldwherethelinear 0 K,eff fitofthelow-fieldanomalousHallresistanceandthelinearfitofthe high-fieldanomalousHallresistanceintercept.

For PHE measurements, a dc current and magnetic field are applied along the x direction (in the plane of the sample), and the voltage along the y direction isrecorded asthe fieldis swept from μ H=0.7Ttoμ H=−0.7T.Thelow-fieldplanarHallvoltageisfittothe 0 0 equation69:
R H=R 0 1(cid:1) μ H 0 x (1) 0 K,eff
whereR isascalingfactorandμ H istheeffectiveanisotropyfield, 0 0 K,eff givenbyμ H =μ (M +H?)(whereH? istheperpendicularani- 0 K,eff 0 s K K sotropy field). μ H is defined as positive when the film has in- 0 K,eff plane anisotropy, and negative when the film has perpendicular anisotropy.

Out-of-plane ferromagneticresonancemeasurementswereperformed on filmstodetermine the Gilbertdamping using a flip-chip setupwithacoplanarwaveguide.TheappliedDCmagneticfieldwas sweptwithafixedfrequencyRFfield,andthechangeinmicrowave absorptionwithfieldwasrecorded.Dataforeachfrequencyisfittoa Lorentzianderivativepeak,whichprovidesthelinewidth.Thewidthof thispeakisrelatedtotheGilbertdampingαofthefilmbythefollowing equation:
μ ΔH =μ ΔH + 4πα f (2) 0 FMR 0 0 γ
whereγ isthe gyromagnetic ratio and μ ΔH is the zero-frequency 0 0 linewidth. The zero-frequency linewidth is directly related to the inhomogeneityinthemagneticpropertiesofthefilm.

Brillouinlightscattering
WeemployedastandardBrillouinlightscatteringsetupusingasix-pass, tandem Fabry-Pérot interferometer. The incident laser with a wavelengthof532nmand60mWpowerwasfocusedontothesample using a 50 mm lens. The lens was situated in an optical setup that enabled rotation of the sample in the Damon-Eschbach spin wave geometry with minimal movement of the laser spot on the sample surfaceandminimalchangeinfocusfromthelens.Thesamplewas rotatedbetween5°and77°(k=2μm−1−3μm−1),andthesetupprovidedanangularresolutionof0.002°.

SIMSmeasurements
SIMSanalysiswasperformedusinganelectrostaticquadrupolesec- ondary ion mass spectrometer (Hiden Analytical EQS-MS). This wasequippedwithanAr+ionsourceatanionenergyof1kV(−35nA ionbeamcurrent)andasampleareaof1mm ×1mmwith200pixels × 200pixelswasscanned.Theionbeam(withadiameterof100μm) followed a raster pattern during each etching cycle. Each etching cycle corresponds to the removal of a thin layer of the film, giving adepthprofile.Onequarterofthescannedareawasselectedasthe analytical area. An electron flood source (FS40, PREVAC) was used throughout the measurement for charge compensation. The CoGd ferrimagneticfilmsusedforSIMSanalysishadthesamecomposition describedin“Synthesis”,butweregrownonaSisubstratecoatedwith 100 nm of LPCVD SiN to limit any O− ion contributions from the substrate.

Modelingofthermalproperties
The thermal response of metallic thin filmswas modeled using the “Heattransferinsolids”(ht)packageofCOMSOLMultiphysics.The temporalheatprofileduetolaserannealingwassimulatedbyinputtingthermalpowertothetopsurfaceofthinfilmsandobservingthe temperature changes induced through the film and substrate. The thermalpropertiesofeachmaterialweredefinedusingthematerials libraryprovidedinCOMSOLMultiphysics.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "I am disappointed that my recommendation to divide this work into separate papers was not adopted. The comprehensive\nnature of a review requires all questions to be addressed, and when multiple separate experiments are involved, this\nnecessitates resolving each issue independently yet simultaneously—a considerably difficult task. I would advise focusing\non a single material system. The current analysis of various material systems appears insufficient, lacking thorough\nquantitative discussion. To put it simply, the authors merely enumerate experimental results without providing meaningful\ninsight into their significance or underlying mechanisms. The explanations seem to consist primarily of listing numerous\npossibilities. Unfortunately, as long as this structure combining three or four disparate experimental results persists, even if\nsome experiments show promising results, the presence of less coherent experiments or discussions will undermine the\noverall cohesiveness of the research. I again recommend dividing this work into separate papers for submission to more\nspecialized journals.\nAs an expert in laser annealing crystallization, magnetic materials, and spin waves, I find numerous perplexing aspects and\ninsufficient evidence for drawing conclusions in these discussions, preventing me from recommending publication. The\npoints raised below primarily indicate a lack of necessary data, which would require additional peer review after\nsupplementary data is provided.\nWhile some results not specifically addressed in my comments below may be valuable, I will refrain from commenting on\nthose aspects.\nComments on Specific Sections\nSection 1: Controlling Structural Transformations with DWLA\n-. This section appears to be primarily introductory and instructional in nature. No claims of novelty are made, and indeed, I\nsee no novel contribution here. The authors should clearly indicate which aspects are superior to or consistent with previous\nresearch. The connection between this section and subsequent discussions should also be explicitly established.\nSection 2: Tuning Magnetic Properties with DWLA\n-. Regarding Figure 3a, please clarify the validity of the magnetization measurements. The authors should provide a\ndiscussion of the coercivity magnitude, saturation magnetization values, and analyze the CoGd sublattice states. Without\nsuch context, it is difficult to assess the reliability of these results. The statement that \"these behaviors are characteristic of\nferrimagnets in the vicinity of a change in the dominant magnetic sublattice, which can be the result of a change in thickness,\ntemperature, or in this case, chemical composition [44, 45]\" seems insufficiently substantiated.\n-. Concerning the CoFeB/MgO heterostructure results, previous literature has already demonstrated similar outcomes comparing laser annealing to furnace annealing in other material systems. Simply presenting the technique therefore lacks\nnovelty. The authors should quantitatively demonstrate which specific aspects of their findings are definitively new. I do not\ncurrently discern significant novelty or interest in these results. The manuscript transitions to different material systems\nbefore thoroughly examining important aspects such as surface roughness changes, interface conditions, elemental\ndiffusion at interfaces, and MgO insulating properties.\nSection 3: Large-area Tunable Anisotropy Gradients for Magnonics\n-. The computational model is not provided, making the calculation results incomprehensible.\n-. Figures 4a, 4b, and 4c lack clear explanation of what the different shades represent.\n-. What appears in Figure 4 seems to be spin wave propagation bands rather than band gaps. Band gaps typically appear\nwithin propagation bands. To properly discuss magnonic crystals introduced by laser-induced magnetization changes,\nstructures with varying periodicity should be compared. Comparing differences when changing the laser gray scale gradient\nlevels would also be valuable. Given the BLS technique used, mapping propagation characteristics in all directions would\nbe useful for evaluating the effectiveness of this method. Overall, the claims, experiments, and analysis are not well aligned.\n-. Figures 4b and 4c cannot be considered equivalent. Spin wave propagation bands can be freely changed by the\nmagnitude of the effective magnetic field, so this alone is insufficient to demonstrate agreement between experimental and\ncalculated results. Several inconsistencies are puzzling: calculation spectra are curved while experimental spectra are\nstraight; band gaps do not appear within propagation bands; and despite using BLS, evaluation is only done in specific\ndirections. The configuration in Figures 4a, 4b, and 4c appears to be for surface waves, while Figure 4d seems to be for\nvolume waves, which is also puzzling.", "reviewer_2": "I appreciate all the efforts made by the authors to address mine and other reviewer's comments, improve the readability, and,\nmore importantly, add new data to make the manuscript more compelling and highlight novelty. I was also please to see the\nmagnonic channel demonstration! I am therefore happy to recommend this paper for publication as is.", "reviewer_3": "The authors have addressed many of the concerns raised by all the reviewers in the first round of reviews, making the ‘take-\nhome message’ of their manuscript clearer to the reader. Overall the manuscript is well written and the figures are well\nformulated. However, there are some issues that remain which should be addressed before it is ready to be published.\n1) Some of the points that the authors stressed in their rebuttal letter as being addressed in the new manuscript are either\nonly briefly touched upon, or somewhat hidden within the methods section of the manuscript. For example, the authors\nperformed COMSOL simulations to determine materials parameters (affinity for oxidation, thermal conductivity of the\nsubstrate, layer thicknesses, etc…) which are important in determining the appropriate sample design to achieve a particular\ntemperature profile, and therefore the desired magnetic properties. These design principles must be considered to fully\nrealize the power of their technique, but are largely overlooked in the current main text of the manuscript, even though they\nhave been explored by the authors.\n2) The point of Figure 2 is to highlight the physical phenomena (crystallization, oxidation, and interdiffusion) which are the\ndominant mechanisms in each material system investigated. How do the authors rule out that each case does not result from\na combination of these 3 phenomena? Perhaps this could be addressed by elaborating more on my concern in point 1.\nSome of the materials characterization provided is perhaps a bit lacking in rigor. The appearance of diffraction spots in the\nelectron diffraction patterns is hard to see, it seems like a rather subtle effect, the authors only show a small range of 2theta\nvalues in the XRD scans – why was this range chosen – because this is the range where the most intense diffraction peaks\nfor all the phases are observed? Or would we learn more by seeing a wider range of 2theta values presented in the\nextended material? Could SIMS analysis be performed for the interdiffusion samples to show the depth profiles are changed\nby the intermixing? That seems like the more straightforward method for demonstrating interdiffusion.\n3) While the authors have removed one type of material system from their manuscript, there are still four systems to keep\ntrack of. I recommend that the authors use consistent notation throughout the manuscript to make sure it is clear to the reader\nwhich system is being discussed. In particular, different notations are used for the Co/Cr and Co/Ta-based heterostructures,\nwhich are also referred to as SAFs, and Co/Cr/Co films. The authors should also clarify if Si/SiO2 substrates were used\nthroughout the figures (as stated in the methods section) or whether the CoGd films were grown in SiN substrates as\nindicated in the figure caption to Figure 2."}, "author_response": "We are grateful to the reviewers for taking the time to read our updated manuscript and for offering\nconstructive feedback. For the reviewers’ convenience, we have included a version of the revised main\ntext with our changes tracked in our resubmission.\nBased on feedback from the reviewers, we have added new supplementary data to quantitatively support\nour conclusions associated with the physical transformation mechanisms and to substantiate our\ncomparison of micromagnetic simulations and BLS data for our magnonics application. Furthermore, we\nhave significantly reorganized the Supplementary Information to provide structure and clarity as to which\nmaterials and physical properties are being discussed. The new section titles and, where relevant, the\nmajor new content additions are as follows:\n• Section S1: Modeling laser-induced heating of thin films\n• Section S2: Clarifying competing physical transformations in material systems\n• Section S2.1: CoFeB Ferromagnets\no XRR data for CoFeB/MgO ferromagnetic films after DWLA exposure using\nvarious laser fluences, indicating that the interfacial roughness is not affected\nby the annealing process.\no SQUID-VSM characterization demonstrating that the saturation magnetization\nis not impacted by DWLA, indicating that the films are not significantly oxidized\nduring DWLA.\n• Section S2.2: CoGd Ferrimagnets\no XRD measurements indicating that the crystalline structure of our CoGd films is\nunaffected by DWLA.\n• Section S2.3: CoFeB/Pt/Ru SAFs\no Wide-range XRD measurements demonstrating that no additional structural\nphases are induced by DWLA.\n• Section S2.4: Co/X/Co (X = Cr, Ta) SAFs\no SIMS characterization of a Co/Cr/Co-type structure before and after DWLA,\nindicating intermixing of the Co and Cr layers\no XRD characterization of a Co/Ta/Co-type structure exhibiting no appreciable\nchange in the crystalline structure after DWLA.\n• Section S3: Further magnetic characterization of films\n• Section S4: Spin-wave propagation in CoFeB\no Details of the micromagnetic simulations of spin wave propagation, including\ncomparisons between experimental versus simulated data for specific\nwavevectors and data on propagation of spin waves orthogonal to the gradient\nstripes.\n2\n• Section S5: Unprocessed images of domain wall motion in CoFeB/Pt/Ru SAFs\n• Section S6: Further characterization of DWLA\nWe respond point by point to the reviewers’ specific comments below. We believe that, with these\nchanges, our manuscript is ready for publication in Nature Communications.\nRESPONSE TO REVIEWE RS' COMMENTS\nReviewer #1 (Remarks to the Author):\nI am disappointed that my recommendation to divide this work into separate papers was not adopted.\nThe comprehensive nature of a review requires all questions to be addressed, and when multiple\nseparate experiments are involved, this necessitates resolving each issue independently yet\nsimultaneously—a considerably difficult task. I would advise focusing on a single material system. The\ncurrent analysis of various material systems appears insufficient, lacking thorough\nquantitative discussion. To put it simply, the authors merely enumerate experimental results without providing\nmeaningful insight into their significance or underlying mechanisms. The explanations seem to consist\nprimarily of listing numerous\npossibilities. Unfortunately, as long as this structure combining three or\nfour disparate experimental results persists, even if\nsome experiments show promising results, the\npresence of less coherent experiments or discussions will undermine the overall cohesiveness of the\nresearch. I again recommend dividing this work into separate papers for submission to more specialized\njournals.\nWe carefully considered the suggestion to divide the work into separate papers, and it would certainly\nhave been a valid approach. Our decision to keep this paper intact was based on conversations with\nresearchers in the community who expressed interest in the breadth and generality of the technique,\nwhich can be readily applied to various materials targeting different heat-assisted material changes. To\nclarify this motivation, we have included a discussion of our design principles and the rationale behind our\nchoice of these materials at the beginning of our Results section and in the discussion of structural\ntransformations.\nThroughout the paper, we have clarified the mechanism responsible for the physical transformation of\nour thin films, and we have added supplementary data to support a conclusive dominant mechanism of\nstructural transformation. Finally, we have emphasized the significance of the stated results where\nappropriate. We hope that the Reviewer will understand our motivation to keep the manuscript in this\nform.\nAs an expert in laser annealing crystallization, magnetic materials, and spin waves, I find numerous\nperplexing aspects and insufficient evidence for drawing conclusions in these discussions, preventing me\n3\nfrom recommending publication. The points raised below primarily indicate a lack of necessary data, which\nwould require additional peer review after supplementary data is provided.\nWhile some results not specifically addressed in my comments below may be valuable, I will refrain from\ncommenting on those aspects.\nComments on Specific Sections\nSection 1: Controlling Structural Transformations with DWLA\n-. This section appears to be primarily introductory and instructional in nature. No claims of novelty are\nmade, and indeed, I see no novel contribution here. The authors should clearly indicate which aspects are\nsuperior to or consistent with previous research. The connection between this section and subsequent\ndiscussions should also be explicitly established.\nWe agree with the reviewer that the “Structural Transformation” section of our manuscript primarily\nillustrates that DWLA can induce physical changes that can indeed occur in response to other\ntreatments, including furnace annealing, ion irradiation, and localized oxidation. This section of our\nrevised manuscript, whose content was guided by questions raised by all reviewers during the first\nround of review, now illustrates a key thesis of our work: DWLA offers a universal and widely available\ntechnique capable of enacting disparate physical transformations in different magnetic thin films and\nproviding gradients in the magnetic properties in complex patterns. To clarify this point, we have\nincluded additional text to this effect in the introductory paragraph of this section. Furthermore, the\n“Structural Transformation” section has been modified to include additional citations to studies in which\ntechniques other than DWLA were used to achieve similar physical transformations in magnetic thin\nfilms.\nSection 2: Tuning Magnetic Properties with DWLA\n-. Regarding Figure 3a, please clarify the validity of the magnetization measurements. The authors\nshould provide a discussion of the coercivity magnitude, saturation magnetization values, and analyze\nthe CoGd sublattice states. Without such context, it is difficult to assess the reliability of these results.\nWe agree with the reviewer that there are other possible routes by which the coercivity or net saturation\nmagnetization of a TM-RE ferrimagnet could be modified without a variation in the saturation\nmagnetization of one or both elemental sublattices. For example, if laser annealing increases the\nroughness of the ferrimagnet, this could lead to an increase in coercivity. However, under the reasonable\nassumption that the degree of roughness would scale with the laser fluence used, this scenario is\nincompatible with the nonmonotonic trend we observe in the coercivity as a function of laser fluence.\nRegarding the magnitude of the magnetic parameters we measure, we note that while the saturation\nmagnetization does indeed approach zero in the vicinity of the magnetic compensation temperature, it is\nthe trend in the coercive field, rather than precise magnitudes, that defines a divergence in the coercivity.\nhighly emblematic of magnetic compensation in a ferrimagnet, we agree that such behaviors do not\ndirectly indicate a change in the magnetically dominant elemental sublattice. We can draw such a\nconclusion by focusing on the sign of the Kerr rotation observed during our MOKE hysteresis loop\nmeasurements. As detailed in the Methods section of our revised manuscript, MOKE measurements\nconducted using visible light are primarily sensitive to the magnetic orientation of the TM sublattice. As\nsuch, the fact that we observe a change in the MOKE loop polarity following application of laser fluences\non either side of the divergence in coercivity, or a minimum in saturation magnetization, concretely\nillustrates that these trends are linked to a change in the magnetically dominant elemental sublattice.\nWhile our SIMS analysis does not differentiate between O- ions originating from Co or Gd, RBS\ncharacterization of CoGd ferrimagnets has conclusively demonstrated that Gd oxidizes much more readily\nthan Co [Z. Liu et al., PRB 107, L100412 (2023)] supporting our observation that DWLA-induced oxidation\nprovides a means of tuning the Gd sublattice magnetization, and thus, the ferrimagnetic properties of our\nCoGd films.\nConsidering the above points, we have modified Figure 3a to include inset MOKE loops measured for laser\nfluences on either side of the divergence in coercivity. This addition demonstrates that the divergence in\ncoercivity we observe with increasing laser fluence occurs concomitant to a change in the magnetically\ndominant sublattice. Furthermore, we have modified our discussion of the CoGd system in the “Tuning\nmagnetic properties” section to denote which observed behaviors suggest a change in the dominant\nsublattice and which behaviors directly indicate such a change.\nThe statement that \"these behaviors are characteristic of ferrimagnets in the vicinity of a change in the\ndominant magnetic sublattice, which can be the result of a change in thickness, temperature, or in this\ncase, chemical composition [44, 45]\" seems insufficiently substantiated.\nTo address the reviewer’s concerns, we have revised the referenced statement to include additional\ncitations to studies where a change in the dominant magnetic sublattice of a ferrimagnet was inferred\nfrom features such as divergent coercivity, nonmonotonic trends in saturation magnetization versus\ntemperature, or a reversal in MOKE loop polarity. We also cite examples where these behaviors arise from\npost-growth treatments, including ion irradiation, oxygen plasma, and furnace annealing. In line with our\nresponse to the reviewer’s previous comment, these additions clarify that the magnetic property\nvariations we observe in response to DWLA are consistent with the known effects of post-growth\nprocessing (including oxidation) and can yield results comparable to those achieved by modifying the\ngrowth parameters, such as thickness or TM–RE proportionality.\nConcerning the CoFeB/MgO heterostructure results, previous literature has already demonstrated similar\noutcomes comparing laser annealing to furnace annealing in other material systems. Simply presenting\nthe technique therefore, lacks novelty. The authors should quantitatively demonstrate which specific\n5\naspects of their findings are definitively new. I do not currently discern significant novelty or interest in\nthese results.\nWe agree with the reviewer that the effect of laser annealing on CoFeB/MgO heterostructures has been\ndemonstrated (with the effect on exchange bias reported in A. Sharma et al, IEEE Transactions on\nMagnetics (Volume: 55, Issue: 1, January 2019)). This heterostructure is one of the systems shown due to\nits familiarity, where the effects of thermal annealing on magnetic properties as a function of temperature\nare well-known. This justifies our understanding of the effect of laser annealing in our systems as a\nthermally driven transformation. Here, the transformation is not new, but the ability to generate gradients\nin the properties in complex designs over large areas and the demonstration of applications in magnonics\nis new. To emphasize the novelty in this particular system, we have rephrased the discussion in the\n“Physical transformation” section to clarify what is novel and what is already known.\nThe manuscript transitions to different material systems before thoroughly examining important aspects\nsuch as surface roughness changes, interface conditions, elemental diffusion at interfaces, and MgO\ninsulating properties.\nIn the main text, we have highlighted the dominant transformation mechanisms in our system. We have\nnow added further physical characterization and explanation to the Supplementary Information for all\nfilms, considering changes in the surface roughness and interdiffusion. X-ray reflectivity measurements of\nCoFeB films indicate minimal changes in interface quality over the range of fluences studied. Oxidation of\nthe CoFeB would decrease the saturation magnetization. In the fluence range providing PMA, we do not\nobserve any decrease in the saturation magnetization. At fluences above the range of PMA, we do see a\ndecreased magnetization, which may indicate oxidation. In CoFeB/Ru/Pt- and Co/Cr/Co-based SAFs, we\ndo observe interface interdiffusion, as shown in Sections S2.3 and S2.4 of the Supplementary Information,\nrespectively. In CoGd ferrimagnets, as mentioned above, we do not observe a systematic decrease in the\nsaturation magnetization as a function of laser fluence, which would suggest diffusion of Pt and Ta into\nthe magnetic layer. The additional data that we have added to the Section S2 of the Supplementary\nInformation provides a more thorough examination of these film properties.\nWe verified that our MgO is insulating by measuring the 2-point resistance of a continuous 2.5 nm MgO\nfilm. This two-point resistance was >10 MOhm over 1 mm distance, confirming its insulating state.\nAdditionally, while the insulating nature of MgO is essential for magnetic tunnel junctions, we consider\nthe electrical properties of our films to be outside the scope of this work.\nSection 3: Large-area Tunable Anisotropy Gradients for Magnonics\n-. The computational model is not provided, making the calculation results incomprehensible.\nThe mumax3 code for the model will be provided in the Zenodo repository, and we have attached the\ncode to the resubmission for the convenience of the reviewer. Additionally, a description of the\ncomputational model is now included in Section S4.1 of the Supplementary Information.\n6\n-. Figures 4a, 4b, and 4c lack clear explanation of what the different shades represent.\nMany thanks to the reviewer for pointing this out. Legends have now been added to Figure 4.\n-. What appears in Figure 4 seems to be spin wave propagation bands rather than band gaps. Band gaps\ntypically appear within propagation bands. To properly discuss magnonic crystals introduced by laser-\ninduced magnetization changes, structures with varying periodicity should be compared. Comparing\ndifferences when changing the laser gray scale gradient levels would also be valuable. Given the BLS\ntechnique used, mapping propagation characteristics in all directions would be useful for evaluating the\neffectiveness of this method. Overall, the claims, experiments, and analysis are not well aligned.\nIndeed, this is a demonstration of spin wave propagation bands, rather than demonstrating a band gap.\nWe would not expect a band gap for this geometry, given that the spin waves travel along the gradient\nstripes and thus do not experience a periodic change in magnetic properties as would be the case for a\nmagnonic crystal. We agree that the tunability of this is important; we have simulated changing the\ngradient levels (see Supplementary Figure S15), but we did not create multiple samples in an effort to\nmove forward with resubmission.\nWe are slightly confused by the reviewer’s comment to evaluate spin wave propagation bands in more\ndirections. We can interpret this either as that they would like to see spatially resolved measurements\nusing micro-focused BLS, or that they would like to see the spin wave propagation orthogonal to the\nstripes. Concerning the first interpretation, we only performed wave vector-resolved BLS, which does not\nhave the spatial resolution to measure spin waves propagating in different directions. Additionally, micro-\nfocused BLS does not have the wave vector resolution required to see these propagation bands, as the\nwave vector resolution is defined by the collection angle of the objective lens, which is intrinsically very\nlarge considering its numerical aperture. We now mention in the main text that we have wavevector\nresolution but not spatial resolution.\nRegarding the second interpretation of this comment, we have added data and micromagnetic simulation\nfor the propagation of spin waves orthogonal to the gradient stripes into the Supplementary Information\n(see Section S4.2). Simulating this geometry is difficult because the environment is locally asymmetric but\nhas translational symmetry. In the simulation, spin waves are excited from a 10 nm linear source and\npropagate from that region (shown schematically in the new Supplementary Fig. S12). However, in the\nBLS experiment, all the spin waves excited within the >30 um laser spot are measured. Thus, comparison\nbetween experiment and theory is less reliable compared to the geometry shown in the main text. We\nnote there may be more appropriate modeling tools [O. Wojewoda et al, Phys. Rev. B 110, 224428 (2024)],\nwhich are beyond our expertise.\nNevertheless, we can still compare the simulated and measured spectra for this geometry. Qualitatively,\nwe observe that there is a single defined peak for both simulation and experiment in contrast to the wide\nplateau seen for the other geometry. Quantitatively, the spin wave frequency is 1.5 GHz higher than the\nmeasured spin wave frequency (shown in the left panel in the figure below). This offset can be corrected\n7\nfor by adding a uniaxial in-plane anisotropy in addition to the uniaxial out-of-plane anisotropy. A uniaxial\nin-plane hard axis along the stripes with an anisotropy energy of K =4.3x104 J m-3 (implemented using a\nIP\ncustom field in mumax3) shifts the simulated frequency peak to match that of the experimental data\n(shown in the right panel in the figure below). For a direct comparison, all spectra are at k = 9.7 rad μm-1\nfor 𝜇 H = 0.35 T.\npattern created in a similar CoFeB sample, which reveals strikingly different hysteresis loops when\napplying the field along the stripes and orthogonal to the stripes (see figure below). This difference\nconfirms that there is an in-plane anisotropy in addition to the out-of-plane anisotropy. This makes sense\nbecause the written pattern is also very different along the two in-plane directions. The asymmetry of the\nloops for positive and negative magnetic field is due to the limited magnetic field range in our MOKE\nmagnetometer, which means we cannot fully saturate the film in-plane. Because of this, we cannot extract\nthe value of the anisotropy field from these MOKE loops. Still, the hysteresis loops provide evidence that\nan in-plane anisotropy component is appropriate to include in simulations. Including this anisotropy term\ndoes not affect the spin wave dispersion along the stripes because there is no magnetization component\nalong the hard axis in this case.\nis sufficiently captured by simulations. The same anisotropy landscape is used for simulations of spin\nwaves traveling along and orthogonal to the stripes, and both simulations are comparable to experimental\ndata. Thus, this provides additional evidence that this technique is effective in producing designed\nmagnetic landscapes. The data and discussion above have been added to the Supplementary Information\nsection 4.2 and Supplementary Fig. S14.\n-. Figures 4b and 4c cannot be considered equivalent. Spin wave propagation bands can be freely changed\nby the magnitude of the effective magnetic field, so this alone is insufficient to demonstrate agreement\nbetween experimental and calculated results. Several inconsistencies are puzzling: calculation spectra are\ncurved while experimental spectra are straight; band gaps do not appear within propagation bands; and\ndespite using BLS, evaluation is only done in specific directions.\nThank you to the reviewer for pointing out possible inconsistencies in the presented data. First, regarding\nthe shape of the calculated vs measured spectra, this can be explained by our estimation of the exchange\nstiffness and the reduced signal-to-noise ratio at higher k values in BLS. We have updated our exchange\nstiffness to 10 pJ m-1 in simulations (a value experimentally measured in CoFeB films by J. Cho et al, JMMM\n339, P. 36-39 (2013)), which now more accurately reflects the experimental dispersion. In addition, we\ncompare the FFT/BLS intensity vs frequency for several fixed k values for both techniques, seen below.\nHere, it is observed that the simulation and experiment agree very well for all k values, with only small\ndifferences observed on the shoulders of the peaks. The reduced number of counts at high k values means\nthe signal-to-noise ratio is lower, leading to less sharp transitions from the signal to background. In the\nexperiment, we are also measuring a small spread of wavevectors due to the collection angle of the\nfocusing lens, which might also slightly alter the shoulders of the measured peaks. Finally, the saturation\nmagnetization of the measured sample could be marginally lower than that of the simulated sample. This\nwould modify the dipolar contribution to the dispersion and flatten the bands. We have added the\nfollowing data to Section S4.2 of the Supplementary Information (Supplementary Fig. S13), as we agree\nthis quantitative comparison is important to the results.\nAs mentioned above, we have also added data and micromagnetic simulation for the propagation of spin\nwaves orthogonal to the gradient stripes to the Supplementary Information.\nfor volume waves, which is also puzzling.\nIn Figure 4d, the ferromagnetic resonance mode is measured, and the linewidth from this uniform mode\nis plotted as a function of frequency. Because in-plane ferromagnetic resonance measurements are\nsusceptible to contributions from magnon scattering, leading to possible error in the extracted Gilbert\ndamping value, the magnetic field was applied out-of-plane. This damping value is a material parameter\nthat is also relevant to the propagation of surface waves.\nReviewer #2 (Remarks to the Author):\nI appreciate all the efforts made by the authors to address mine and other reviewer's comments, improve\nthe readability, and, more importantly, add new data to make the manuscript more compelling and\nhighlight novelty. I was also please to see the magnonic channel demonstration! I am therefore happy to\nrecommend this paper for publication as is.\nThank you to the reviewer for spending the time to review the revised manuscript. We appreciate their\nrecommendation to publish the paper in Nature Communications.\nReviewer #3 (Remarks to the Author):\nThe authors have addressed many of the concerns raised by all the reviewers in the first round of reviews,\nmaking the ‘take-home message’ of their manuscript clearer to the reader. Overall the manuscript is well\nwritten and the figures are well formulated. However, there are some issues that remain which should be\naddressed before it is ready to be published.\n1) Some of the points that the authors stressed in their rebuttal letter as being addressed in the new\nmanuscript are either only briefly touched upon, or somewhat hidden within the methods section of the\nmanuscript. For example, the authors performed COMSOL simulations to determine materials parameters\n(affinity for oxidation, thermal conductivity of the substrate, layer thicknesses, etc…) which are important\nin determining the appropriate sample design to achieve a particular temperature profile, and therefore\nthe desired magnetic properties. These design principles must be considered to fully realize the power of\ntheir technique, but are largely overlooked in the current main text of the manuscript, even though they\nhave been explored by the authors.\nWe thank the reviewer for this suggestion to enhance our take-home message to the reader. We have\nnow moved the discussion of design principles to the main text, both at the beginning of the results\nsection, and we have highlighted strategic materials choices in the “Physical transformation” section.\n10\n2) The point of Figure 2 is to highlight the physical phenomena (crystallization, oxidation, and\ninterdiffusion) which are the dominant mechanisms in each material system investigated. How do the\nauthors rule out that each case does not result from a combination of these 3 phenomena? Perhaps this\ncould be addressed by elaborating more on my concern in point 1.\nIndeed, we employed specific sample design principles to give a single dominant physical transformation\nin response to heat. For example, the diffusion of Ru as a function of annealing temperature has been the\nsubject of many studies due to its use in MTJ structures. It is typically thermally stable up to 400 °C. In\naddition, CoFeB/Pt multilayers were found to have significantly decreased PMA after annealing at 350 °C.\nThus, there is a process window where we can create interdiffusion of CoFeB/Pt without causing Ru\ninterdiffusion. We have now added more detailed descriptions of how we made such choices to the\nphysical transformations. We have also added new x-ray reflectivity and SQUID-VSM data and associated\ndiscussion to the Supplementary Information to complement our claim of a single dominant physical\ntransformation in each material system.\nIn the case of the CoGd ferrimagnets, we acknowledge that a change in the degree of crystallinity of the\nlayers of our heterostructure may accompany the oxidation detected in response to DWLA, which could\nalso modify the magnetic properties. To probe any changes in the crystallinity of the structure, we\nperformed XRD measurements of a CoGd film before and after treatment with DWLA. As is typical for\namorphous CoGd ferrimagnets, the as-grown film only exhibits a broad peak corresponding to the (111)\npolycrystalline texture of the Pt seed layer and an intense, narrow peak corresponding to the Si (004)\nreflection of the substrate. After uniform DWLA treatment, no new peaks become apparent, indicating\nthat the CoGd layer remains macroscopically amorphous. Furthermore, the width of the rocking curve\ncollected about the Pt (111) reflection does not show a substantial change after DWLA treatment,\nsignifying that the polycrystalline texture of these layers is not affected by the annealing process. Potential\nchanges in the crystallinity of the RKKY spacer layer in our Co/X/Co (X = Cr, Ta) SAFs were also assessed by\nperforming XRD on a Ta film before and after DWLA. As with the CoGd ferrimagnet, we observe no\nevidence of new crystalline phases or any change in the polycrystalline texture of Ta following DWLA.\nThe measurements discussed above have been incorporated as new Supplementary Figs. S2, S3, S5, and\nS8, and a discussion of the results with appropriate citations has been added to the oxidation portion of\nthe “Physical Transformation” section of the main text.\nSome of the materials characterization provided is perhaps a bit lacking in rigor. The appearance of\ndiffraction spots in the electron diffraction patterns is hard to see, it seems like a rather subtle effect,\nThe reviewer is correct that we should add context to the TEM of CoFeB films. The electron diffraction\nspots are indeed weak, reflecting the textured nature of the CoFeB/MgO interface, which is typical in this\nheterostructure [J. Liu et al, Appl. Phys. Lett. 107, 232408 (2015)]. Nonetheless, this onset of crystallization\nis sufficient to impact the magnetic anisotropy dramatically. We have added this reference and a short\ndescription to the discussion of the TEM to explain our results better.\n11\nthe authors only show a small range of 2theta values in the XRD scans – why was this range chosen –\nbecause this is the range where the most intense diffraction peaks for all the phases are observed? Or\nwould we learn more by seeing a wider range of 2theta values presented in the extended material?\nYes, the XRD data is shown in the 2theta range where we observe diffraction peaks from the film. An XRD\nscan of a larger range is now added to the Supplementary Information as Supplementary Fig. S6, where\nthe Si substrate peak is also visible at 2theta = 69.25 degrees. We have also added an explanation of why\nthis range was chosen to the description of the XRD data in the main text.\nCould SIMS analysis be performed for the interdiffusion samples to show the depth profiles are changed\nby the intermixing? That seems like the more straightforward method for demonstrating interdiffusion.\nBased on the referee’s suggestion, we performed SIMS characterization of a Co/Cr bilayer sample before\nand after DWLA treatment. The measurements show that, following DWLA, Co appears much earlier\nduring the etching process, and there is a broad range of etch cycles over which strong signals from both\nCo and Cr are detected, indicating that DWLA causes Co to diffuse into the Cr layer. These measurements\nhave been included in the revised Supplementary Information as Supplementary Fig. S8a.\n3) While the authors have removed one type of material system from their manuscript, there are still four\nsystems to keep track of. I recommend that the authors use consistent notation throughout the manuscript\nto make sure it is clear to the reader which system is being discussed. In particular, different notations are\nused for the Co/Cr and Co/Ta-based heterostructures, which are also referred to as SAFs, and Co/Cr/Co\nfilms. The authors should also clarify if Si/SiO2 substrates were used throughout the figures (as stated in\nthe methods section) or whether the CoGd films were grown in SiN substrates as indicated in the figure\ncaption to Figure 2.\nWe have updated our notation for different films to be consistent throughout the text. Indeed, the only\nfilm grown on SiN was the CoGd film used for SIMS, because we wanted to avoid any oxygen signal from\nan SiOx-coated substrate. However, all other films are grown on Si/SiOx. This point is now clarified in the\nMethods section.\nREVIEWERS' COMMENTS\nReviewer #1 (Remarks to the Author):\nFinally, content has been provided that reveals the results. I believe sufficient information has been\nprovided for each experiment. I would have preferred this information to be provided from the\nbeginning. I think it has reached a level suitable for publication.\nWe appreciate the reviewer’s suggestions to help make our results more convincing and thank them\nfor their recommendation that the manuscript is ready to be published.\nReviewer #3 (Remarks to the Author):\nThe authors have addressed the concerns from the reviewers about the lack of data to support their\nclaims about what the laser technique is doing to the samples. I still have some concerns about the\nlarge number of samples which are described in the manuscript, with the majority of the real\n'science' relegated to the supplemental material.\nWe are happy to hear that the reviewer believes we have addressed the stated concerns. We chose\nto address many samples to demonstrate the versatility of the technique and, while much of the\nmaterials science can be found in the Supplementary Information, we have ensured that all results\nare referred to in the main text."}, {"round": 2, "reviewer_comments": {"reviewer_1": "Finally, content has been provided that reveals the results. I believe sufficient information has been provided for each\nexperiment. I would have preferred this information to be provided from the beginning. I think it has reached a level suitable\nfor publication.", "reviewer_3": "The authors have addressed the concerns from the reviewers about the lack of data to support their claims about what the\nlaser technique is doing to the samples. I still have some concerns about the large number of samples which are described\nin the manuscript, with the majority of the real 'science' relegated to the supplemental material."}, "author_response": ""}]

Decision letter