bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epitaxial Growth of fee Fe and Cu Films on Diamond
Authors: Pappas D.P. , Glesener J.W. , Harris V.G. , Krebs J.J. , Idzerda Y.U. , Morrish A.A. , Prinz G.A. 
Published: September 2012

ABSTRACTThe growth of iron and copper films and multilayers on the (100) face of diamond has been achieved and studied by reflection high energy electron diffraction (RHEED), extended x-ray absorption fine structure (EXAFS), ferromagnetic resonance (FMR), and SQUID Magnetometry. RHEED and AES studies show that 2–3 atomic layers (AL) of Fe on C (100) forms a continuous film. The films as deposited at room temperature are disordered, and after a 350° C anneal displays a face-centered cubic structure. Subsequent layers of Cu on this epitaxial Fe film grow as an oriented, single crystal fee film. FMR and SQUID signals have been observed from the Fe films, showing that they are ferromagnetic.
Magnetic Ordering of Mn Overlayers on Fe (100)
Authors: Walker T. G. , Hopster H. 
Published: September 2012

ABSTRACTSpin polarized electron energy loss spectroscopy (SPEELS) was used to probe the magnetic state of mn over layers on Fe (100). Nonzero exchange asymmetries are measured and found to oscillate with a two monolayer period as the mn overlayer thickness is varied, proving that the surface layer of the mn overlayers has a net magnetic moment and that these (100) Magnetic layers are aligned antiferromagnetically. The average exchange splitting of the mn surface layer is found to be 2.9 eV, indicating that the mn surface has a magnetic moment of the order 3 μg. In addition, oxidized mn overlayer surfaces have been studied, and the spectral features in the range 0 to 6 eV energy loss can be assigned to 3d-3d transitions of Mn2+. No indication of magnetic ordering of the MnO overlayer has been oserved.
Structural and Magnetic Properties of e-Beam Prepared CoxPt1-x Alloy Films
Authors: Harzer J.V. , Hillebrands B. , Pogosova I.S. , Herrmann M. , Güntherodt G. , Weller D. 
Published: September 2012

ABSTRACTWe have investigated structural and magnetic properties of CoPt alloy films with strong perpendicular magnetic anisotropy in the thickness range between 100Å and 400A. From a detailed x-ray analysis we find highly (111) -textured CoPt Microcrystal-lites in all samples. STM studies reveal a granular topography with grain diameters of up to 250Å. Measurements of hysteresis loops yield a saturation field which increases with thickness, and which is consistent with a freely mobile domain Model. Brillouin light scattering measurements of the frequencies of the surface and standing spin wave modes yield a bulk exchange constant, which is strongly dependent on the Pt content.
Magnetoresistance and Structure of Granular Co/Ag Thin Films
Authors: Stearns Mary Beth , Cheng Yuanda 
Published: September 2012

ABSTRACTSeveral series of CoxAg1-x granular thin films (-3000Å) were fabricated by coevapora-tion of Co and Ag in a dual e-beam UHV deposition system at varying substrate temperatures. These films have low field magnetoresistance values as large as 31% at room temperature and 65% at liquid N2 temperature. The structure of the films was determined using magnetization measurements as well as x-ray and various electron microscopy techniques. The composition was determined using Rutherford backscattering spectroscopy. The Magnetoresistance was measured at both room and liquid N2 temperatures.We deduce from the magnetization and RBS Measurements that the films consist of Co globules embedded in a Ag Matrix and that there is no appreciable mixing of the Co and Ag atoms in the films deposited at substrate temperatures ≥ 400°K. The size of the Co globules is seen to increase with increasing Co concentration and the maximum magnetoresistance occurs in those films having the smallest Ag thickness which provides magnetic isolation of the Co globules.We suggest that the large magnetoresistance of these films arises from the same mechanism which causes the low field magnetoresistance in pure ferromagnets, namely, the scattering of the highly polarized d conduction electrons of the Co at magnetic boundaries. The large increase in the room temperature magnetoresistance of the CO/Ag films as compared to those of pure 3d ferromagnetic films is due to the distance between the magnetic boundaries being reduced to a few nanometers, because of the small size of the single domain Co globules, as compared to a few microns in 3d ferromagnets.
Giánt Mr in Granular Systems Prepared by Melt-Spinning and Sputtering
Authors: Dieny B. , Teixeira S.R. , Rodmacq B. , Chamberod A. , Genin J.B. , Auffret S. , Gerard P. , Redon O. , Pierre J. , Ferrer R. , Barbara B. 
Published: September 2012

ABSTRACTWc report the observation of giant magnctorcsistance in granular systems prepared by either Melt-spinning or sputtering. For Melt-spun CoxCu1-x alloys, with x varying between 5 and 30%, Magnctoresitancc amplitudes of 20% in 50 kOc at 5 K were obtained, similar to those reported for the same alloys prepared by sputtering. For sputtered (Ni80Fe20)xAg1-x alloys, three different contributions to the magnetorcsisiancc have been clearly identified: The spin-valve (or giant) Magnctorcsistance, scattering on magnetic fluctuations, and anisotropie Magnetorcsistancc. These three contributions have their own dependences on the size of the magnetic particles, on the degree of intermixing between NiFe and Ag, and on the temperature. In the third scries of samples, sputtered (Co70Fe30)xAg1-x, very large magnctorcsistance amplitude has been observed (AR/R as high as 20% at room temperature in 10 kOc and 60% at 10 K).
Giant Magnetoresistance in Granular Ni81Fe19/Ag Formed from Annealed Multilayers
Authors: Bian X. , Zaluska A. , Altounian Z. , Ström-Olsen J.O. , Huai Y. , Cochrane R.W. 
Published: September 2012

ABSTRACTWe have observed giant Magnetoresistance (GMR) in Ni81Fe19/Ag granular structures synthesized by the annealing of artificial multilayers made by sputtering. The size and morphology of the magnetic precipitates can be controlled by adjusting the magnetic layer thickness in the initial stage. Magnetoresistance as large as 30% was found at 4.2 K with a rather small saturation field. Giant Magnetoresistance in this alloy system essentially depends on the magnetic precipitate size, annealing temperature and the Ni81Fe19 concentration. The temperature dependence of the magnetoresistance in these films is discussed.
Growth Temperature Dependence of magnetoresistance in Co/Cu (111) Wedged Superlattices
Authors: Harp G. R. , Parkin S. S. P. , Farrow R. F. C. , Marks R. F. , Toney M. F. , Lam Q. H. , Rabedeau T. A. , Cebollada A. , Savoy R. J. 
Published: September 2012

AbstractThe Magnetoresistance of MBE deposited Co/Cu (111) superlattices as a function of Cu layer thickness is studied at various growth temperatures. Wedged superlattices are fabricated with uniform Co layers but with Cu layers whose thickness varies with position along the length of the substrate. Cu thickness is varied over the range 7–75Å. Only one Maximum M Magnetoresistance (MR) is observed for a Cu layer thickness ∼ 10Å for all growth temperatures studied (0°, 150°, 200°C). The optimal magnetoresistance values are achieved with 150°C growth temperature.
Giant Magnetoresistance and Structure of Phase-Segregated Epitaxial Metals
Authors: Marks R.F. , Farrow R.F.C. , Harp G.R. , Parkin S.S.P. , Rabedeau T.A. , Toney M.F. , Cebollada A. , Thangaraj N. , Krishnan Kannan M. 
Published: September 2012

ABSTRACTGiant Magnetoresistance, GMR, in thin metal films elicits attention due to its technological potential as well as its relevance to theory of exchange coupling. Epitaxial, phase-segregated ferromagnet/paramagnet Mixtures have been grown by UHV evaporation. Such films show spontaneous formation of ferromagnetic clusters, leading to large values of GMR (40% at room temperature) as grown. The growth of Co-Cu, Co-Ag, Fe-Ag and Permalloy-Ag films are described. Structural analysis by grazing-incidence small angle X-ray scattering (GISAXS) provides a measure of cluster size and characteristic spacing. Effects of growth temperature and subsequent annealing on GMR and film structure are described. Preliminary results of TEM examination of (001) Fe-Ag and Co-Ag granular films are presented for the first time.
Perpendicular Magnetoresistance in Cu/Co and Cu/(NiFe) Multilayers
Authors: Schroeder P. A. , Bass J. , Holody P. , Lee S.-F. , Loloee R. , Pratt W. P. , Yang Q. 
Published: September 2012

ABSTRACTThe Magnetoresistance Measured perpendicular to the plane of the Multilayer, (CPP-MR) has been measured for the Cu/CO and Cu/ (Ni/Fe) systems. The predictions of a two spin-channel model are summarized, and the Cu/CO data are analysed in terms of this theory. The Cu/ (NiFe) data show a more complex behaviour.
New BCT Iron Phase in (100) Felr Superlattices
Authors: Andrieu S. , Hübsch J. , Piecuch M. , Hennet L. , FISCHER H. 
Published: September 2012

ABSTRACTIn this paper, the synthesis of a new structure of iron in (100) Felr superlattices grown by Molecular Beam Epitaxy is reported. Two-dimensional growth up to 4 planes at 400K occurs, as shown by RHEED oscillations. Electron diffraction also gives evidence that the Fe lattice is pseudomorphic to the Ir one during the 2D-growth, and relaxes to the bcc lattice for thicker deposits. An X-Ray analysis shows that the Fe structure is a body centered tetragonal one with a c/a ratio close to 1.25. This phase is observed to be non-Magnetic at room temperature, as a weak ferromagnetic behaviour is observed at low temperatures, except at small Ir thicknesses. This is the evidence of the existence of a low spin phase which seems to undergo a second order phase transition with the atomic volume of iron.
Epitaxial Ferromagnetic MnGa and (MnNi) Ga Thin Films with Perpendicular Magnetization on GaAs
Authors: Tanaka M. , Harbison J.P. , Sands T.D. , Philips B.A. , De Boeck J. , Cheeks T.L. , Florez L.T. , Keramidas V.G. 
Published: September 2012

ABSTRACTWe have successfully grown thermodynamically stable ferromagnetic MnxGa1-x (x=0.55∼0.60) thin films with thicknesses ranging from 3 nm to 60 nm on GaAs substrates by molecular beam epitaxy. The c-axis of the tetragonal structure of the MnGa film is shown to be aligned perpendicular to the substrate. Both Magnetization Measurements and extraordinary Hall effect measurements indicate perpendicular magnetization of the MnGa films, exhibiting squarelike hysteresis characteristics. Furthermore, we have investigated the effect of Ni additions as a substitution for mn in (Mn60-yNiy) Ga40 alloy thin films with y=0 – 30 at% Ni. With increasing Ni, the perpendicular component of the magnetization becomes smaller up to y=18 where the magnetization is in-plane. At y=30, the magnetization is again perpendicular.
Studies of Magneto-Optical Recording in Multi-Magnetic-Layer Disk by Analytic and Simulating Approaches
Authors: Kawazoe Yoshiyuki , Hu Xiao , Honma Shigeru 
Published: September 2012

ABSTRACTThe effect of magnetic coupling in Multi-layer system is discussed by an analytic approach and computer simulation. The dependence of the enhancement of external field on the magnetic properties of the relevant materials is studied. Comparison between the theoretical estimate, simulation result and experimental observations are presented.
Anomalous Perpendicular Anisotropy in Ultra-Thin Co Films
Authors: Wiedmann Michael H. , Engel Brad N. , Van Leeuwen Robert A. , Mibu Ko , Shinjo Teruya , Falco Charles M. 
Published: September 2012

ABSTRACTWe have used in situ polar Kerr effect measurements to study the magnetic coercivity and anisotropy of MBE-grown Pd (111) /Co/X and Au (111) /Co/X trilayers, where χ is the nonmagnetic noble or transition metal overlayer Ag, Cu or Pd. Polar hysteresis curves were Measured in situ for systematically varied Co and overlayer thicknesses 2 Å ≤ tco ≤ 20 Å and 0 Å ≤ tx ≤ 50 Å. We find the coercivity and total anisotropy display a strongly peaked perpendicular contribution at ∼1 atomic layer (2 Å) non-Magnetic Metal coverage. For Cu, where the effect is strongest, the total anisotropy energy rapidly decreases by a factor of 3 from its peak value after a total coverage of ∼2 atomic layers (4 A) of Cu.
Spin-Resolved Photoemission Study of n = 2 Core Levels of Iron
Authors: Klebanoff L.E. , Van Campen D.G. , Pouliot R.J. 
Published: September 2012

ABSTRACTThe first spin-resolved x-ray photoelectron spectroscopy (SRXPS) study of the n = 2 core levels of ferromagnetic Fe are reported. The 2p3/2, 2p1/2and 2s core levels all display interesting spin-dependent structures and splittings. The spectral complexity predicted by a purely atomic picture is not observed in the data. The results indicate that theories incorporating the delocalization of the 3d valence band are more applicable to the description of core-level photoemission in iron.
Giant Magnetoresistance Calculated from First Principles
Authors: Butler W. H. , MacLaren James M. , Zhang X.-G. 
Published: September 2012

ABSTRACTThe Layer Korringa Kohn Rostoker-Coherent Potential Approximation technique was used to calculate the low temperature Giant Magnetoresistance from first principles for Co|Cu and permalloy|Cu superlattices. Our calculations predict large giant Magnetoresis-tance ratios for Co|Cu and extremely large ratios for permalloy|Cu for current perpendicular to the layers. Mechanisms such as spin-orbit coupling which mix spin channels are expected to greatly reduce the GMR effect for permalloy|Cu.
Spin-Polarization in Ultrathin Rh Layers on Fe (001)
Authors: Chouairi A. , Dreysse H. , Nait-Laziz H. , Demangeat C. 
Published: September 2012

ABSTRACTThe origin of the Rh polarization at the interface with Fe is discussed within a self-consistent mean-field parameterized tight-binding model. Since experimentally it is not yet known how Rh grows on Fe (001), in this paper we consider both fee and bec growth. When Rh grows in the fee structure, it expands its lattice parameter and a polarization is present up to 3 layers, whereas in the bec case only the Rh atoms at the interface are polarized. The results obtained are compared to recent spin- and angle-resolved photoelectron spectroscopy experiments. Good agreement with experiment is obtained in the case of a fee Rh configuration.
Magnetic Order of Fe and Co on Cu (001)
Authors: Haroun A. , Chouairi A. , Ouannasser S. , Jensen P.J. , Bennemann K.H. , Dreysse H. 
Published: September 2012

ABSTRACTWe determine the initial growth mode of Co and Fe on Cu (001). In the monolayer range Co and Fe present a clear trend to form clusters on Cu (001). Supposing a perfect epitaxy and fee lattice, the magnetic moment distribution is determined by using a tight binding Hubbard-like Hamiltonian. The influence of the temperature is taken into account in order to compare the theoretical predictions with experimental results.
Magnetic Circular Dichroism in X-Ray Absorption and Core-Level Photoemission
Authors: Tobin J.G. , Waddill G.D. , Gouder T.H. , Colmenares C.A. , Pappas D.P. 
Published: September 2012

ABSTRACTHere is reported observation of magnetic circular dichroism in both x-ray absorption and core-level photoemission of ultra thin magnetic films using circularly polarized x-rays. Iron films (1–4 ML) grown on a Cu (001) substrate at 150 K and magnetized perpendicular to the surface show dramatic changes in the L2,3 absorption branching ratio for different x-ray polarizations. For linearly-polarized x-rays perpendicular to the magnetic axis of the sample the branching ratio was 0.75. For films ≥ 2 ML, this ratio varied from 0.64 to 0.85 for photon spin parallel and anti-parallel, respectively, to the magnetic axis. This effect was observed either by changing the x-ray helicity for a fixed magnetic axis, or by reversing the magnetic axis for a fixed x-ray helicity. Our observation can be analyzed within a simple one-electron picture, if the raw branching ratios are normalized so that the linear value becomes statistical. Furthermore, warming the films to -300 K eliminated this effect, indicating a loss of magnetization in the film over a temperature range of -30 K. Finally, reversing the relative orientation of the photon spin and the magnetic axis from parallel to anti-parallel allowed measurement with photoemission of the exchange splitting of the Fe 2p and 3p core levels which were found to be 03 eV and 0.2 eV, respectively. These results are consistent with earlier studies, but the use of off-plane circularly-polarized x-rays from a bending magnet monochromator offers -2 orders of magnitude greater intensity than typical spin-polarization measurements. Finally, we have performed preliminary x-ray absorption studies of UFe2, demonstrating the feasibilty of MCD Measurements in 5f as well as 3d Materials.
Evidence for Spin Polarization of Metallic Copper in CO/Cu and Fe/Cu Multilayers
Authors: Pizzini S. , Giorgetti C. , Fontaine A. , Dartyge E. , Krill G. , Bobo J.F. , Piecuch M. 
Published: September 2012

ABSTRACTMagnetic circular x-ray dichroism measurements on CO/Cu and Fe/Cu Multilayers at the K edge of copper show that the 4p -states of copper are significantly spin-polarized by the adjacent magnetic layers. In relation to the phase opposition of the copper thickness-dependent magnetoresistance of CO/Cu and Fe/Cu Multilayers it is of prime importance to notice that the polarization of the conduction electrons of copper follows specifically the polarization of the conduction electrons of the adjacent magnetic element.
Hyperfine Fields in Ultrathin Fe and FeAu Alloy Films on Au (111)
Authors: Brockmann M. , Pfau L. , Lugert G. , Bayreuther G. 
Published: September 2012

ABSTRACTMagnetic properties of ultrathin Fe and Fe60Au40, alloy films on Au (111) were studied by SQUID Magnetometry and conversion electron Mössbauer spectroscopy. In order to get information on the influence of interdiffusion, iron films with thin alloy zones at the interfaces to Au have been prepared by co-evaporation of iron and gold and compared with iron films with presumably sharp interfaces. It was found that the presence of an 0.5 ML (Mass coverage in Monolayer) alloy zone reduces the effective magnetic interface anisotropy field and affects the growth mode of a subsequently deposited iron film such that the film is more sensitive to annealing. Groundstate Magnetic Moments and hyperfine fields are significantly enhanced in Fe/Au(111) (tFe ≤ 4 ML) and Fe60Au40 films, compared to bulk Fe.
Modeling Giant Magnetoresistance and Relative Permeability in Granular Films
Authors: Parker M.R. , Barnard J.A. , Hossain S. , Seale D. , Tan M. , Waknis A. 
Published: September 2012

ABSTRACTA Model for the field dependence of giant Magnetoresistance (GMR) in ‘granular’ co-sputtered alloy thin films (based on a relatively simple spin-dependent scattering concept appropriate to superparamagnetic and weakly ferromagnetic films) is applied to new experimental data from the Co90Fe10-Ag system. The Model and the experimental data can be shown to compare very well with the help of a single adjustable parameter related to spin correlation of adjacent Co-Fe clusters. A careful fit of field-dependent MR data and theory leads to a fairly reliable determination of spin-cluster radius. An analysis of the relative permeability of granular GMR films derived from the generalized form of the Clausius-Mossoti relationship is also presented. For a non-Magnetic Matrix the effective relative permeability is shown to be materials independent. The permeability model is applied to Co-Au granular films.
Polarized Neutron Reflectivity Measurements of Collinear and Non-Collinear Magnetic Structures in Fe/Cr (100) Superlattices
Authors: Ankner J.F. , Schleyer A. , Zeidler Th. , Majkrzak C.F. , Zabel H. , Wolft J.A. , Grünbergt P. 
Published: September 2012

ABSTRACTWe have used polarized neutron reflectivity to study the magnetic microstructure of two Fe/Cr (100) superlattices grown by molecular beam epitaxy. The first film, of nominal composition [0.9 nm Cr/5.5 nm Fe]5, and atomically sharp interfaces, exhibits classical collinear antiferromagnetic structure. The other film ([1.2 nm Cr/5.5 nm Fe]5), grown at a higher temperature, shows the field-dependent non-collinear features attributed to biquadratic coupling. We will describe these measurements and our preliminary structural analysis.
Neutron Scattering Study of Antiferromagnetic and Ferromagnetic Coupling in Ni/Ag Multilayers
Authors: Rodmacq B. , Burlet P. , Mangin Ph. , Hennion M. 
Published: September 2012

ABSTRACTIndirect Magnetic coupling in sputtered Ni/Ag Multilayers has been recently studied by magnetization and magnetoresistance techniques. These experiments indicate that coupling is anti ferromagnetic through 11 and 30 A of silver, and probably ferromagnetic through 20 Å. We present here direct evidence for such a magnetic coupling for all three thicknesses, as obtained from low angle neutron scattering experiments. Multilayers in which the Ag layer thickness is either 11 or 30 Å both exhibit a supplementary diffraction peak at a q value corresponding to twice the chemical period. Its evolution with both temperature and applied field confirms its purely magnetic origin. In order to study the coupling through 20 Å of silver, we prepared a multilayer in which the Ag layers are alternately 11 and 20 Å thick. In this case, we also observe a doubling of the chemical period. The coupling through 11 Å being anti ferromagnetic, this unambiguously shows that the coupling through 20 Å is ferromagnetic.
Magnetic and Magneto-Optic Properties of dc Magnetron Sputtered Co-Cr/Al Multilayers
Authors: Auner G.W. , Naik R. , Rao U.M. , Zhao Y. , Wang B. 
Published: September 2012

ABSTRACTSingle layers of Co82?l8 with thickness in me ranee of 100–1500Å and multilayers of Co-Cr/Al with Co-Cr thickness in the range of 100–200A and Al at 7Å were prepared by dc magnetron sputtering. The films were deposited on to Si (111) and glass substrates at room temperature. A 100Å thick Al buffer layer was deposited to improve the c-axis orientation. X-ray diffraction (XRD) Measurements on the multilayers show a predominant Co-Cr (00.2) peak. Polar Magneto-optic measurements were performed to determine the Kerr rotation (θK) and figure of Merit. The results indicated an enhancement in the figure of merit at λ = 632.8 nm for the multilayered structures compared to single layer samples. All of the films show a 4πMs value around 6 kG and ferromagnetic resonance measurements indicate an enhancement in the perpendicular anisotropy field for the 150Å multilayered sample.
Giant Magnetoresistance in Sputter-Deposited Granular Ag-Co Thin Films
Authors: Lee W. Y. , Deline V. R. , Gorman G. , Kellock A. , Miller D. , Neiman D. , Savoy R. , Vazquez J. , Beyers R. 
Published: September 2012

ABSTRACTGiant Magnetoresistance (GMR) is reported in as-deposited Ag1−xCox (x = 0.26–0.53) films co-sputtered on Si from separate Ag and Co targets. GMR ratios (10 K Oe Maximum field) exceeding 0.50 and 0.19 at 5 and 295 K, respectively, are observed for the Ag067Co033 films deposited at ≃28 to 175 °C. The Maximum ratios of 0.55 and 0.24 occur at a substrate temperature of ≃125 °C for these films. The ratios decrease rapidly for the films deposited at temperatures > 175 °C and reduce to ≃0.15 and 0.04 at deposition temperatures >300 °C. This deposition temperature dependence of GMR ratios is interpreted in terms of the change in the spin-dependent interfacial electron scatterings due to the change in the size and number of ferromagnetic Co particles within the electron mean free path. The initial increase and the subsequent decrease in GMR ratios with increasing deposition temperature are attributed to the increase in the mean free path, and the Co and Ag particle size, respectively. Changes in mean free path are obtained from the resistivities of these films while changes in Ag and Co particles are deduced mainly from the X-ray diffraction patterns, transmission electron Micrographs, and the coercivities of these films.