bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic and transport properties of amorphous FeAuB films
Authors: McGuire T. R. , Aboaf J. A.
Published: February 2003

Magnetic and galvanomagnetic properties are given for amorphous FexAu0.8−xB0.2 films and are compared to crystalline FeAu films. The amorphous alloys show a magnetic moment per Fe which is 10% to 25% less than in the crystalline alloys where Fe has the normal value of ≊%2.2μB. This decreases is attributed to boron and comparable to the decrease found in amorphous FeB. The Hall effect as given by the Hall conductivity Rs/ρ2 is about the same value [∼0.03 (Ω cm G)−1] in both the crystalline and amorphous systems for higher Fe concentrations x≳0.62. As Fe becomes more dilute the Hall conductivity drops to about 0.02 (Ω cm G)−1. The anisotropic magnetoresistance Δρ at room temperature has a maximum value of Δp≊0.57×1006 Ω cm in amorphous FeAuB, about 30% higher than in the crystalline alloy. In general, however, the galvanomagnetic properties seem to be insensitive to the structure of the alloys.
Spin waves in amorphous Fe1−xBx alloys
Authors: Rhyne J. J. , Fish G. E. , Lynn J. W.
Published: February 2003

The temperature dependence of spin excitations has been studied in amorphous Fe1−xBx (x = 0.18 and 0.14) by inelastic neutron scattering. The spin-wave stiffness constant D was determined directly from the magnon dispersion curves (E = Dq2) over the temperature range from below room temperature (T/TC = 0.48 and 0.36, respectively, for x = 0.18 and 0.14 alloys) up to 548 K (T/TC = 0.75 and 0.99), which is just below the crystallization temperature. For both alloys the temperature dependence of D was found to be proportional to (T/TC)5/2 up to (T/TC) greater than 0.8. The extrapolated values of D at T = 0 were D = 167 and 138 meV A2, respectively, and were nearly twice as large as those determined from the T3/2 coefficient found from magnetization studies. These anomalies may be related to the Invar characteristics of the thermal expansion in these alloys. Limited data were also obtained for an alloy Fe76B24 which exhibits a higher D (≳174 meV A2).
d magnetism in the amorphous Y-Co, Y-Ni, and Y-Fe alloys
Authors: Gignoux D. , Givord D. , Liénard A.
Published: February 2003

In this paper we describe the magnetic properties of Y-M amorphous alloys (M = Fe, Co, Ni) in which only 3d magnetism is involved. When the properties are not strongly dependent on environment effects, they are similar to those observed in the corresponding crystalline alloys: (i) Y-Co and Y-Ni alloys exhibit ferromagnetism when the 3d moment is large; (ii) far from the critical concentration for the disappearance of magnetism, the decrease of the 3d moment with increasing Y-concentration is similar in amorphous and crystalline alloys; (iii) near the critical concentration, very weak itinerant ferromagnetism may be observed in amorphous Y-Ni alloys as well as in the crystalline ones. On the contrary, the properties which are dependent on environment effects are strongly affected by the amorphous state: the properties of metamagnetism of itinerant electrons, which are very important in crystalline Y-Co alloys near the critical concentration, lead in the amorphous state to a persistence of a mean 3d moment at much higher concentrations due to the diversity of environments; Y-Fe alloys are spin-glasses due to competing positive and negative magnetic interactions which in R2Fe17 compounds lead to helimagnetic structures.
Metallic glasses under pressure: Mössbauer studies
Authors: Bouzabata B. , Ingalls R. , Rao K. V.
Published: February 2003

The Mössbauer effect was used to study amorphous Fe27Ni53P14B6, Fe29Ni49P14B6Si2, Fe30Ni45P16B6Al3, and Fe32Ni36Cr14P12B6 up to pressures of 100 kbar. Pressure is found to decrease the Curie temperature and average hyperfine magnetic field at the iron sites. The effect of pressure on the width of the hyperfine field distribution and isomer shift is also described.
Abstract: Electrical and magnetic properties of amorphous PdCuSiFe alloys
Authors: Herlach D. M. , Wassermann E. F. , Kästner B. J.
Published: February 2003

We have measured the ac suscepbility χ and the resistivity ρ of splat cooled amorphous Pd77.5−xCu6Si16.5Fex alloys (0<x<15 at.%). The zero field susceptibility of alloys with x = 1 to 5 at.% Fe exhibits a single cusp at the freezing temperature Tf = 3 K/at.% Fe indicating spin-glass-like behavior below Tf. In additional magnetic dc fields the cusp is first rounded and then split, presumably due to ferromagnetic fluctuations above Tf. This is concluded from the strong increase of χ with x and marked deviations from a simple Curie Weiss law for χ above Tf. Alloys with x = 10 and 15 at.% Fe exhibit both ferromagnetic and spin-glass behavior. In zero field a steep rise of χ with decreasing temperature is followed by a sharp cusp at TC = 61 and 131 K, respectively, near the PM-FM transition. At lower temperatures around Tf, the decrease of χ with temperature indicates a gradual freezing into the spin-glass state. The different behavior of χ near the transitions is also reflected in its different field dependences. The resistivity of all alloys shows a Kondo-like anomaly at low temperatures, decreasing in size with increasing x. The influence of a magnetic field on ρ(T) varies in a similar way with x. The magnetoresistance is negative and much larger than the low T anomaly of ρ for x≳5 at.% Fe. From this and from the absence of any distinct behavior of ρ around Tf and TC we infer that the resistivity besides a structural contribution is predominantly caused by single spin scattering.   *Work supported in part by SFB 125, West Germany.
Amorphous GdCo disk for thermomagnetic recording
Authors: Togami Y. , Kobayashi K. , Kajiura M. , Sato K. , Teranishi T.
Published: February 2003

Thermomagnetic recording was carried out on 150-mm-diam amorphous GdCo disks rotated at a speed of 1800 rpm. GdCo films showing good uniformity were deposited on glass disks by rf sputtering technique. Bits as small as 1 μm in width were recorded, making use of compensation temperature with a laser power of 5.6 mW and were read out with a laser power of about 2 mW. Thermal stability and dependence of the Kerr rotation angle on wavelength were also measured. It was confirmed that GdCo film is a most promising material for thermomagnetic recording.
Influence of O2 and N2 addition on the perpendicular magnetic anisotropy of Gd-Co amorphous films
Authors: Hoshi Y. , Naoe M. , Yamanaka S.
Published: February 2003

The influence of the introduction of oxygen gas and nitrogen gas into the chamber during deposition on the perpendicular magnetic anisotropy of Gd-Co amorphous films deposited by ion beam sputtering has been investigated. The films deposited without O2 and N2 addition show perpendicular magnetization in the vicinity of compensation composition. However, the perpendicular anisotropy of them is much smaller than that of the films deposited by rf sputtering. When sputtering ion energy, deposition rate, and Ar pressure are 0.5∼3 keV, 19∼30 Å/min, and 8×10−3∼8×10−2 Pa, respectively, the films obtained have almost the same perpendicular anisotropy. On the other hand, the incorporation of oxygen in the films leads to a remarkable increase of perpendicular anisotropy. The films deposited at O2 pressure of 1.6×10−3 Pa have an effective perpendicular anisotropy constant K⊥(K⊥ = Ku-2πMs2) of about 5×105 erg/cm3, where Ku is 1.1×106 erg/cm3. On the contrary, the incorporation of nitrogen decreases the perpendicular anisotropy. The incorporation of oxygen and nitrogen leads to the considerable shift of compensation composition to the Gd rich region and phase separation. These results may be attributable to preferential oxidization and nitrification of Gd.
Magnetically determined particle alignment factors of sintered rare-earth cobalt permanent magnets
Authors: Searle C. W. , Davis V. , Hutchens R. D.
Published: February 2003

Values for the particle alignment factor have been obtained, during the past few years, by several workers.1, 2, 3, 4 The various techniques which have been used include magnetic, x-ray, and optical experiments. However, particle alignment factors are not now routinely obtained during the processing of permanent magnets. There is a requirement for ’’real time’’ feedback for production purposes, and there is also a requirement for a magnetic probe of structure for a basic understanding of these sintered permanent magnets. For these reasons we have decided to consider various magnetic determinations of the particle alignment for SmCo5 permanent magnets.
Annealing of rapidly quenched sendust ribbon
Authors: Tsuya N. , Arai K. I. , Ohmori K. , Homma T.
Published: February 2003

The effect of the heat treatment on the coercive force of Sendust ribbon for the contemporary recording head use prepared by a rapid quenching roll method was examined under various conditions. The room temperature coercive force was decreased when the ribbon was cooled slower than the rate of 103 deg/h and quenched below 800 °C. The lowest coercive force 8 mOe was observed for the ribbon cooled at the rate of 60 deg/min and quenched at 550 °C.
Exchange striction and crystal lattice in domains and domain walls
Authors: Pascard H. , Globus A.
Published: February 2003

The role of the exchange striction energy in ferrimagnetic materials is reported: (a) A relation between the exchange striction ’’volume anomaly’’ ΔV/V and the sublattice magnetizations is deduced from molecular field theory and is confronted with experiment. (b) A relation between the magnetoelastic anisotropy term ΔK specific to the polycrystalline state and the product of the exchange stresses by the magnetostrictive strain is established from experiment, on the basis of a previously proposed mechanism. (c) A relation between the crystal lattice parameter a and the magnetization states in magnetic domains and domain walls is proposed.
Synthesis of Mn-Zn ferrite from Na2O-B2O3 flux under CO-CO2 ambients
Authors: Plaskett T. S. , Shivashankar S. A. , Gilbert B. L. , Olson B. L. , Chien C.-L. , Herman D. A.
Published: February 2003

Synthesis was carried out by dissolving MnO, ZnO, and Fe2O3 in the molar ratio 0.42:0.44:1.07 in fluxes of Na2O:xB2O3 at 900 °C and slow cooling under ambients of CO-CO2 mixtures; x varied from 1.34 to 2.0 and Co-Co2 from 0.06 to 1.0% CO. The composition and oxidation state of the precipitated ferrite were dependent on both CO content and x. The composition of the ferrite ranged between Mn0.44Zn0.40Fe2.16O4 and Mn0.09Zn0.06Fe2.85O4 and the Fe2+ between 0.16 and 0.85 moles/formula unit. By using reactive gas mixtures, the cation oxidation states were maintained constant during cooling. Mössbauer spectroscopy and coulometric analysis were used to establish that Mn3+ was unstable in the flux in the presence of Fe2+. The results obtained by these experiments establish the optimum conditions necessary to grow Mn-Zn ferrite films by liquid phase epitaxy (LPE). The saturation magnetization of the synthesized material was between 4700 and 5200 G; the Curie temperature increased with Fe2+ from 180 to 490 °C. These properties agree with measurements previously made on LPE films of this material.
Spin-echo NMR study of the atomic site environments in the Fe67Co18B14Si1 metallic glass
Authors: Ford J. C. , Hines W. A. , Budnick J. I. , Paoluzi A. , Pease D. M. , Kabacoff L. T. , Modzelewski C. U.
Published: February 2003

In order to investigate the near neighbor atomic environment and, consequently, the relationship of such environments to the observed magnetoelastic properties, a spin-echo NMR study of the hyperfine field distributions in Metglas 2605 CO (Fe67Co18B14Si1) for various magnetic annealing treatments has been undertaken. Here, initial spectra for the 11B metalloid and 59Co transition metal nuclei, obtained at 4.2 °K and zero magnetic field, are presented along with supplementary magnetization and x-ray diffraction measurements. Upon annealing, a bcc α-Fe phase precipitates first, leaving a residual amorphous phase of lower Fe content. The appearance of such crystalline regions is accompanied by a strong reduction in the magnetomechanical coupling coefficient.
Dragging of stripe domains by a temperature gradient in Metglas 2826 MB (invited)
Authors: Jen S. , Berger L.
Published: February 2003

A steady, collective, translation of all domains has been observed in field-annealed samples subjected to a temperature gradient dT/dx≡102 K/mm. The square samples, of size 1 mm×1 mm×25 μm, are held at one end by a water-cooled copper clamp, while the opposite end is located 0.1 mm from a thin, electrically heated, nichrome wire. Observations by longitudinal Kerr contrast show that the walls move from the hot to the cold end. We use a 60 Hz magnetic field HE parallel to the induced easy axis, to decrease the effective coercivity and facilitate wall motion. A reversal of the sign of dT/dx is found to cause a reversal of the sense of wall motion. Hydromagnetic forces originating from the Nernst-Ettingshausen effect are probably responsible for this ’’thermal domain-drag’’ motion. We extend the existing theory to the case of isolated plane walls. The shape of the boundary surrounding the region of moving walls in the (dT/dx,HE) plane is explained in terms of the non-zero size xc≡2 μm of the potential wells describing wall pinning. In addition, we review the experimental situation concerning the dragging of domains by an electric current in amorphous Gd-Co-Mo and Gd-Co-Au films, and in Co single crystals.
Multiple types of Fe4+ centers in Ca-doped YIG films
Authors: Antonini B. , Blank S. L. , Lagomarsino S. , Paoletti A. , Paroli P. , Tucciarone A.
Published: February 2003

The effect of annealing in reducing atmosphere on Ca-doped YIG films are studied by means of magnetic circular dichroism (MCD) and magnetic linear dichroism (MLD) in the near infrared. The LPE films had ‖110‖ and [100] orientation and the Ca content was about 0.1 atoms/formula unit. The MDC spectra are found to change shape dramatically after the first milder reducing treatments, then a definite and constant shape is acquired, the corresponding amplitude scaling down linearly with absorption until attainment of full infrared transparency. Such a behavior suggests the presence in the films of more than one type of Fe4+ centers which are reduced at different rates during the initial treatments, until a single type eventually prevails. Furthermore, an AVIA experiment indicates that the Fe4+ centers being reduced at a faster rate have markedly different orientational properties than the later ones, with in-plane MLD about 20 times smaller. The results are explained in terms of different acceptor centers being involved in the earlier and later stages of the reducing treatments and are assumed responsible for the recently reported nonlinear behavior and for increasing oxygen-vacancies concentration of the uniaxial anisotropy constant of YIG:Ca films.
Dynamic properties of laser-annealed, Ga-substituted EuYIG bubble films
Authors: Herman D. A. , DeLuca J. C.
Published: February 2003

Laser annealing induced changes in Ga-substituted EuYIG epitaxial bubble films were studied using FMR, bubble statics, SQUID magnetometry, and dynamic bubble translation experiments employing high speed photography. Comparing annealed to as-grown films, domain wall mobility and saturation velocity were observed to increase up to 50% while static coercivity Hcs was reduced by as much as one-third. Both an increase in exchange A and a decrease in damping α appear to contribute to enhanced mobility; we attribute the variations of both A and α to the interchange of Ga and Fe between crystal lattice sites brought about by laser annealing. The mechanism by which Hcs was reduced is less clear, but may follow from the reduction of stress during annealing.
Abstract: Comparison of magnetic and crystalline profiles in He+-implanted Gd,Tm,Ga:YIG
Authors: Speriosu V. S. , Wilts C. H.
Published: February 2003

Profiles of magnetic and crystalline properties in He+-implanted 〈111〉-oriented Gd,Tm,Ga:YIG were obtained using ferromagnetic resonance and x-ray diffraction techniques, respectively. Implantation was done at room temperature several degrees off 〈111〉 axis. One series of samples was implanted with 140 keV He+ at 1.5, 3.0, 4.5, and 6.0×1015 at. cm−2. Another series consisted of three profiles obtained with single, double, and triple energies and doses in the range 30–140 keV and 9.0×1014–3.0×1015 at. cm−2. For the highest dose the maximum changes in magnetic properties were: −3200 Oe in uniaxial anistropy Hk, a 55% decrease in magnetization M, a 65% decrease in exchange constant A, a 20% increase in damping parameter α, and no change in gyromagnetic ratio γ. The maximum perpendicular strain ε⊥ was 1.26% with a corresponding maximum rms random atomic displacement of 0.23 Å. Lateral strain ε∥ was zero. No evidence was found for creation of extended defects. The highest dose was, at most, half of that required to produce amorphousness. Both ΔHk and ε⊥ had a significantly sublinear dependence on dose. The ratio of maximum ΔHk for the 6.0 and 1.5×1015 at. cm−2 was 1.8 instead of 4.0. The corresponding ratio for strain was 2.6. The difference in sublinearity indicates that ΔHk and ε⊥ are not linearly related through magnetostriction. The equation relating ΔHk, M, and ε⊥ can be preserved only by invoking implantation-induced changes in Young’s modulus, Poisson’s ratio, or the magnetostriction.
Extended theory of the coercive force due to domain wall pinning
Authors: Paul D. I.
Published: February 2003

We have enlarged the theory of ferromagnetic domain wall pinning by defects to include large as well as small deviations of the magnetic anisotropy, magnetization, and/or magnetic exchange energy of the defect, from the host material for all values of the defect width. In particular, we obtain results for the coercive force due to such pinning as a function of two dimensionless constants characterizing the defect and of the defect width. We also obtain results for the maximum obtainable coercive force in terms of these parameters. We discuss these results in terms of applications to the Sm2(Co, Cu, Zr, Fe)17 hard magnetic materials.
Microstructures of precipitation-hardened SmCo permanent magnets
Authors: Rabenberg L. , Mishra R. K. , Thomas G.
Published: February 2003

The microstructural features of isothermally aged and step aged and isothermally aged Sm(Co, Cu ,Fe, Zr)7.4 alloys are examined using electron microscopy and x-ray microanalysis. The microstructure is seen to consist of a cellular morphology with twinned rhombohedral 2:17 phase cell interiors, 1:5 phase cell boundaries, and elongated thin platelets with a 1:3 structure. Upon prolonged aging, Zr preferentially goes into the 1:3 phase, Cu to both the 1:5 and the 1:3 phase, and Fe to the 2:17 phase. Isothermal aging at 850 °C facilitates the growth of the cells and the low-temperature step aging facilitates the chemical partitioning of the transition metals. The role of Zr in developing the morphology and the chemical partitioning is discussed.
A thin film head for perpendicular magnetic recording
Authors: Oshiki Mitsumasa , Kawakami Susumu , Ishida Genichi
Published: February 2003

A thin film head of new probe type was fabricated, applicable to perpendicular recording on Co-Cr rigid disks. The head consists of a magnetic film for the main pole and multiturn spiral coils (2 layers, 10 turns) were fabricated on a ferrite substrate. The recording characteristics were measured on 14-in. sputtered Co-Cr disks having a high permeable Ni-Fe back layer. The magnetomotive force for saturation recording was 2 A-T and the output voltage was 0.65 mV at a pole thickness of 4 μm and pole width of 70 μm, at a head to medium spacing of 0.3 μm. The recording density was measured to be 17 kFRPI at a pole thickness of 0.7 μm.
Magnetoresistance in laminated NiFe films
Authors: van Ooyen J. A. C. , Druyvesteyn W. F. , Postma L.
Published: February 2003

A new way of detecting very small magnetic fields is presented, using the magnetoresistance effect of laminated permalloy. The magnetic properties of permalloy/molybdenum/permalloy sandwiches are investigated. It was found that for molybdenum layers above ca. 1000 Å the effect of lamination decreases. Model calculations about the magnetic structures are presented. The calculated results agree with the experimental results.
Analytic description of magnetoresistive read heads
Authors: Ruigrok J. J. M.
Published: February 2003

With the aid of results from transmission line calculations the performance of thin film read heads is described. Domain walls are neglected. We consider two-legged magnetoresistive heads with and without barber-pole stripes.
Arrott-Noakes plots near the Curie temperature of Fe3Pt: Ordered and disordered alloys in high magnetic fields
Authors: Hiroyoshi H. , Hoshi A. , Nakagawa Y.
Published: February 2003

Arrott and Noakes have proposed the following equation of state for the magnetization near the Curie temperature: M1/β = A(T−TC)+B(H/M)1/γ⋅⋅⋅(1), where 1/β = 2.5 and 1/γ = 0.75. In the present report, the M2.5 vs (H/M)0.75 plots (A-N plots) for ordered and disordered Fe72Pt28 alloys are examined in order to clarify the relationship between the magnetic homogeneity and the structural order parameter S. The A-N plots for the alloys with S = 0 and 1 lie on parallel straight lines, being satisfactorily expressed by Eq. (1), since the ideally disordered alloy is magnetically homogeneous as well as the perfectly ordered alloy. On the other hand, the magnetizations of the alloys with 0<S<1 are not fitted to Eq. (1). It is likely that the deviation from the linearity of the A-N plots is a reliable criterion of the magnetic inhomogeneity.
Magnetic moment distribution in Co-V alloys
Authors: Cable J. W.
Published: February 2003

Magnetization and neutron scattering measurements were made on Co-V alloys containing 10, 15, and 20 at.% V to determine the local environment effects on the magnetic moment distribution in this system. The magnetization data agree with earlier results and suggest the presence of some hcp phase in the 10% sample. This was confirmed by the neutron data which showed both fcc and hcp phases in an approximate 4:1 volume ratio for this alloy. The other two samples were single phase fcc but the 15% alloy was disordered while the 20% alloy was ordered in the Cu3Au-type structure with the maximum order consistent with the concentration. In this ordered alloy, the excess Co occupies the V sites. These ’’wrong sited’’ Co atoms have 12 Co nearest neighbors and larger magnetic moments than the ’’properly sited’’ Co atoms which have an average of 8.8 Co nearest neighbors. The average moments associated with these two types of sites were determined from flipping-ratio measurements on the superlattice and fundamental reflections. The values obtained are 0.28 μB/Co for the proper-site atoms and 1.3 μB/Co for the wrong-site atoms. Average moments at the Co and V sites were determined from the diffuse scattering for the 10% and 15% alloys. The results are 1.38 μB/Co and −0.26 μB/V for the 10% sample and 1.05 μB/Co and −0.11 μB/V for the 15% sample.
Abstract: Magnetism of Heusler alloys (Cu1−xCox)2 MnSn
Authors: Uhl E.
Published: February 2003

New quarternary Heusler alloys of composition (Cu1−xCox)2 MnSn (X = 0–1) were prepared single phase with the cubic L21 structure. Magnetic measurements were undertaken in the ferromagnetic region and in case of alloys with a higher Co content in the paramagnetic region, too. Cu rich samples showed a phase transition similar to that in Cu2MnSn on heating. The Curie temperature exhibited a sharp minimum at Cu1.5Co0.5MnSn. This can be explained assuming a superposition of two different types of interaction: one between Co-Mn and Co-Co and the other between Mn-Mn atoms which are both strongly dependent on composition. The Mn-Mn interaction is discussed on the basis of Stearns’ model (indirect di-d1 interaction). Whereas the moment of Mn in Heusler alloys is usually approx. 4 μB it is only 3.6 μB in those with Co which is explained by a certain kind of disorder. Co itself contributed 0.7 μB to the overall moment. A drastic drop of the magnetic moment of Co was found from 0.7 μB in Co2MnSn to 0.3 μB in the quaternary alloys (Cu1−xCox)2MnSn for x as small as 0.05.      a)Work supported by Österreichische Fonds zur Forderung der wissenschaftlichen Forschung.  1E. Uhl and R. Sobczak, Solid State Commun. 39, 655 (1981).  2M. B. Stearns, J. Magn. Magn. Mater. 15–18, 301 (1980).
Low damping (BiYLu)3Fe5O12 films with 0.5 μm bubbles
Authors: Robertson J. M. , Breed D. J. , Algra H. A.
Published: February 2003

Garnet films of composition (BiYLu)3Fe5O12 have been grown on 〈111〉 Gd3Ga5O12, Sm3Ga5O12, and Nd3Ga5O12 substrates by liquid phase epitaxy. The larger lattice parameter substrates were used in order to increase the bismuth concentration in the films. The anisotropy Ku and the saturation magnetization 4πMs data are presented as a function of the Y/Lu ratio in the melt. The maximum anisotropy obtained was 1.5×105 erg cm−3 which is sufficient to support 0.5-μm-diameter bubbles. The ferromagnetic resonance linewidth at 10.1 GHz was measured to be less than 3 Oe. This allows for a domain wall mobility of 600 ms−1Oe−1 in a 0.5 μm bubble film.
AFMR study of CuCl2⋅DMSO: A pseudo-one-dimensional system with ferromagnetic intrachain interactions
Authors: Willet R. D. , Barberis D. , Waldner F.
Published: February 2003

CuCl2⋅DMSO is a linear chain system with strong ferromagnetic intrachain coupling (J/k = 45 K) and significant interchain coupling (J′/k = −1.6 K). It orders three-dimensionally near 5 K and undergoes a spin-flop transition at low fields (3–4 kOe). The AFMR modes have been observed in the temperature range 1.5–5.5 K. In addition, the spin-flop transition has also been observed due to the cut-off of the AFMR signal at the transition field. The easy and hard axes lie in the ac plane of the monoclinic crystal, with the easy axis making an angle of 55° with the chain direction. Interpretation of the data indicates that the system has nearly XY anisotropy, with a rhombic component approximately 5% of the XY anisotropy. It is observed that the spin-flop field increases as the temperature is lowered, from 3200 G at 5.4 K to 4100 kG at 2 K.
EPR and FMR study of (C6H5NH3)2CuCl4: Evidence for two-dimensional spin diffusion
Authors: Willett R. D. , Waldner F.
Published: February 2003

Bis(anilinium) copper tetrachloride, (C6H5NH3)2CuCl4, is a layered perovskite with ferromagnetic intralayer interactions. At high temperature (T≳200 K), the ESR linewidths ΔH are virtually isotropic and increase linearly with temperature. Extrapolation yields ΔH(ϑ, T = 0) = 3.5(3 cos2 ϑ−1)2. The linewidths are assumed to be given by a contribution ΔHsd(ϑ,∞)2, the spin diffusion enhanced linewidth due to anisotropic exchange only, and ΔH(ϑ,T), the linewidth contribution due to the phonon modulation of the exchange anisotropies. The FMR modes were studied in the ab plane at 4.2 K, as well as the temperature dependence of resonance fields for H‖‖a and H‖‖b. Magnetostatic mode excitations, observed in conjunction with the FMR line were found for temperatures below 11 K.
Noncollinearity as a size effect of CrO2 small particles
Authors: Haneda K. , Kojima H. , Morrish A. H. , Picone P. J. , Wakai K.
Published: February 2003

The magnetic structure of small CrO2 particles doped with about 1.2 wt.% 57Fe has been explored by 57Fe Mössbauer spectroscopy as a function of the particle size. Mössbauer spectra, obtained with a longitudinal magnetic field applied, unambiguously establish that a noncollinear structure exists that is most pronounced for the smallest particles. The analysis indicates that a surface effect is the origin of this phenomenon. It follows that a core model proposed earlier for the magnetic structure of CrO2 small particles is warranted.
1-μm bubble propagation errors in single-layered ion-implanted contiguous disk track
Authors: Hidaka Y. , Matsutera H. , Makino H.
Published: February 2003

1-μm bubble propagation errors in ion-implanted contiguous disk devices are investigated in a single-layered (YSmLuBiCa)3 (FeGe)5O12 (111) garnet film. In a good track with 4×4 μm unit cell, there are two main problems: (1) The minimum drive field was generally high, compared with 1/3 HKl, where HKl was named after Lin et al. (2) The bias margin was degraded at higher bias field for high drive field, when ion implantation was heavy. Problem (1) was found to be mainly due to the charged wall nongeneration in the cusps where bubble resided. Problem (2) was found to be due to ‖λ111‖ decrease caused by ion implantation.
Processing techniques for Permalloy field access bubble devices with 5-μm cell periods and submicron gap widths
Authors: Sethna P. P. , Fontana R. E. , Blake T. G. W. , Bullock D. C.
Published: February 2003

The top down planar process1 for the fabrication of Permalloy field access devices was extended from a 6.75×7.50-μm cell2 to a 4.75×5.0-μm cell with no major changes in the processing sequence. Direct step on wafer lithography, ion milling of the Permalloy, and plasma etching of AlCu were used in the device fabrication. Device topology was scaled, reducing the thicknesses of the Permalloy, oxide, and aluminum layers in order to decrease the permalloy-garnet spacing. The results of this work show that Permalloy field access bubble devices with 5.0-μm cells, 0.7-μm gaps, and 1.5-μm control lines can be processed over areas of 0.25–0.5 cm2, giving device capacities of 512 Kbits to 1 Mbit and device bit densities of 2×106/cm2.
Fast 1- and 2-μm bubbles in films with orthorhombic anisotropy
Authors: Breed D. J. , Geus W. de , Voermans A. B. , van Bakel B. A. H.
Published: February 2003

In this paper it will be shown that high bubble velocities can be realized in garnet films with orthorhombic anisotropy for 2-μm as well as for 1-μm bubbles, if bubbles without Bloch lines have been used. Then the maximum velocity is at least 200 ms−1 for 2-μm bubbles and 100 ms−1 for 1-μm bubbles. It appears that bubble diameter and collapse field of these bubbles strongly depend on the value and on the direction of the in-plane field. Small and large bubbles were observed simultaneously in the presence of in-plane fields. Much lower velocities and a strong scatter in the velocity data were observed for bubbles with other wall states.
Radial expansion dynamics of a magnetic bubble domain
Authors: Han B. S. , Thiele A. A. , Humphrey F. B.
Published: February 2003

High-speed laser photography was used in two measurements on the radial expansion dynamics of unichiral, S = 1 magnetic bubbles during and after the application of large 20-, 40-, and 57-Oe expansion pulses. The bubble diameter was photographed at varying intervals after the beginning of a 120-ns pulse and the chirality change resulting from the application of pulses of widths from 17.5 to 120 ns measured. Plots of the probability of chirality change versus pulse width were used to infer the rate of rotation of the magnetization within the wall. Results are compared with the one space dimensional Schryer-Walker model. The features of high-speed initial motion followed by a slower uniform average velocity agree between the model and the data, but the large transients predicted when the pulse leaves the bubble in the unstable Néel wall state were never observed. It is necessary to increase the Gilbert damping parameter a by fourfold in order to get quantitative agreement between the model and the diameter data. The rotation rate of the model and the data agree for the 57-Oe pulse but a fourfold a increase is required at the lower amplitudes.
Abstract: Determination of effective domain-wall masses in bubble garnet films with resonance techniques
Authors: Jantz W. , Argyle B. E. , Slonczewski J. C.
Published: February 2003

Resonant continuous-wave domain-wall oscillations in bubble garnets have recently attracted interest as an innovative research tool. In particular, the effective domain-wall mass me, expected to be significantly different from the infinite flat-wall Döring mass mD, is studied directly by observing small amplitude oscillations with a magneto-optic technique. The necessary restoring-force data are acquired using both theoretical and experimental approaches. For parallel strip patterns, values obtained from the Kooy and Enz theory are verified experimentally by measuring the bias-field dependence of both the resonance frequency ν and the stripe geometry. For bubble lattices, the Höfelt theory is compared with the measured static bubble compliance in lattices of different density. Finally, for isolated bubbles the Callen-Josephs formula and again static compliance data are used. Our measurements and evaluations generally give values of me/mD which lie between 1.3 and 2.0, with higher values observed for parallel stripes. These results compare favorably with considerations based on the influence of surface stray fields on the domain wall structure.      a)Permanent address: Fraunhofer-Institute für Angewandte Festkörperphysik, Eckerstrasse 4, D7800 Freiburg, West Germany.
Degradation of Co-based thin-film recording materials in selected corrosive environments
Authors: Dubin R. R. , Winn K. D. , Davis L. P. , Cutler R. A.
Published: February 2003

Thin-film cobalt alloys were exposed to different corrosive atmospheres at 85 °C. Effects of the atmospheres on magnetic, physical, and surface chemical properties of the thin films were characterized. Relative humidity (RH) was the most important factor in thin-film specimen corrosion.
Superconducting and magnetic interactions in La1.2−xEuxMo6S8 pseudoternary compounds
Authors: Torikachvili M. S. , Maple M. B. , Guertin R. P. , Foner S.
Published: February 2003

Superconducting and magnetic properties of La1.2−xEuxMo6S8 pseudoternary compounds were investigated by means of low-frequency ac and dc magnetic susceptibility measurements under hydrostatic pressure up to 20 kbar and in magnetic fields up to 10 T. At atmospheric pressure, the superconducting transition temperature Tc is a weak function of Eu concentration x for 0?x?0.2, and decreases smoothly with x for x≳0.2, until it vanishes for x≳0.95. Hydrostatic pressure was found to lower Tc in the La-rich compounds and to increase Tc in the Eu-rich compounds. Pressure also induces superconductivity in compounds with x≳0.95 which are not superconducting at atmospheric pressure with maximum Tc’s that are quite high (∼8 K, midpoint) and comparable to the Tc values of other ternary molybdenum sulfides with divalent metal atoms. Magnetization data (dc) on a La0.2Eu1.0Mo6S8 compound revealed a sizable Meissner effect for pressures ≳7 kbar. At atmospheric pressure, the upper critical magnetic field Hc2 for 0<x?0.6 was enhanced above that of La1.2Mo6S8.
Abstract: Antiferromagnetic ordering of GdD2+x and SmD2+x
Authors: Arons R. R. , Schweizer J.
Published: February 2003

The low-temperature magnetic ordering of the nonstoichiometric compounds GdD2+x and SmD2+x for ‖x‖<0.15 has been investigated by neutron diffraction and magnetic susceptibility measurements. It is shown, that both the antiferromagnetic structure and the Néel temperature TN depend strongly on the D concentration. Both for GdD1.93 and for SmD1.85, the magnetic structure is found to be of the type MnO. For higher concentrations, the structure becomes incommensurate with the lattice. For GdD2.00, a helical structure with axis along the 〈111〉 direction is observed. The angle between the moments in the successive (111) layers is found to be 163.8°. For GdD1.93 and GdD2.00, TN values of 20 K and 15.5 K, respectively, are obtained. For SmD2+x, TN is found to be reduced from 9.6 K for x = 0.15 to 8.0 K for x = 0 and to less than 4.5 K for x = 0.15.
The saturation magnetostriction of thin polycrystalline films of iron, cobalt, and nickel
Authors: Klokholm E. , Aboaf J.
Published: February 2003

The saturation magnetostriction λs of Fe, Co, and Ni films was measured by the cantilevered substrate technique. The values of λs, −6.8×10−6 and −38×10−6, obtained for Fe and Ni, respectively, are in accord with bulk published values. A unique value of λs could not be obtained for Co because the sputtered or evaporated Co films were admixtures of face-centered-cubic and hexagonal close packed phases and the magnitude and sign of λ varied with the fcc content. Increasing the substrate temperatures during film deposition decreases the fcc content; however, this also caused the development of a C-axis hexagonal texture normal to the film plane. Annealing the films at ∼500 °C caused a similar but more pronounced texture. Then, because of the uniaxial anisotropy of Co, the films could not be magnetically saturated and the magnetostrictive behavior changed; i.e., the transverse and longitudinal λ were both negative and in some instances the transverse λ was larger than the longitudinal λ.
Optical and magneto-optical study of the magnetic properties of RbFeCl3, RbFeBr3, and disordered materials of intermediate composition
Authors: Bontemps N. , Grisolia C. , Nerozzi M. , Briat B.
Published: February 2003

In magnetically disordered materials, disorder is usually obtained by dilution with nonmagnetic ions. We present here a prospective work on single crystals of RbFeCl3−xBrx (x = 0/0.04/0.2/1/2/3), where magnetic disorder is expected to be induced via the ligands by eventually changing at random the superexchange between Fe2+ ions. We have measured the optical, Raman, and magnetic circular dichroism (MCD) spectra of our crystals. We focus here on the dependence of absorption versus temperature and ligand, with emphasis on the magnetic properties of the chains. For RbFeCl3 and RbFeBr3, the temperature dependence of the absorption follows the general trends predicted by Tanabe et al.; however spin-orbit coupling is shown to restore significant absorption intensity at TN for RbFeCl3. Mixed compounds exhibit a structural disorder as demonstrated by our Raman and optical experiments. Moreover, relying on the absorption data, we conclude that for x = 0.04, 0.2, and 1, the intrachain interaction is not essentially modified, whereas for x = 2 we suggest that magnetic disorder does exist. Finally, our MCD results are briefly mentioned, and their significance is discussed in terms of the magnetic properties of the pure compounds.
Structure and magnetization studies of Ti-substituted Ni0.3 Zn0.7Fe2O4
Authors: Khan D. C. , Misra M. , Das A. R.
Published: February 2003

The effect of addition of Ti4+ under oxidizing atmosphere on the structural and magnetic properties of Ni0.3Zn0.7Fe2O4 is studied. The results of x-ray diffraction, magnetization, and Arrott plot measurements are reported. The data are analyzed on the basis of a three sublattice Yafet-Kittel model.
Abstract: Field-dependent differential susceptibility study of TTF-AuS4C4(CF3)4: Universal aspects of the spin-Peierls phase diagram
Authors: Northby J. A. , Groenendijk H. A. , deJongh L. J. , Bonner J. C. , Jacobs I. S. , Interrante L. V.
Published: February 2003

An applied magnetic field is known to produce novel effects in the phase behavior of magnetoelastic spin-Peierls systems. Hence we report measurements of the differential susceptibility χ and magnetization M in fields up to 40 kOe (4T) on the spin-Peierls compound TTF-AuS4C4(CF3)4 in the temperature region 1.1 K⩽T⩽4.2 K. The range of field and temperature encompasses an interesting phase region, including the zero-field spin-Peierls transition temperature TC(0) = 2.03 K. The measurements of the differential ac susceptibility provide a more sensitive probe of the transition behavior than magnetization measurements. The first definitive evidence for significant deviations from mean-field critical behavior appear in these measurements, and the appropriate criteria for determining the precise location of the transitions are thus provided by the thermodynamic theory of λ transitions. Using the new criteria, qualitative and even quantitative agreement is obtained with current theories of the field dependence of spin-Peierls transitions. A novel contour plot of χac in the H-T plane is shown to be useful for the delineation of the global phase transition behavior. An investigation of the role of relaxation effects in χac relative to the nature of the phase boundaries is conducted. A major feature is the observation of a striking degree of ’’universality’’ in the phase behavior of three spin-Peierls systems, TTF-AuS4C4(CF3)4, TTF-CuS4C4(CF3)4, and MEM-(TCNQ)2. These universal features are preserved through considerable differences in lattice structure and a variation in TC (0) of a factor of 10. A complete report on this work has been submitted to Physical Review B.    a)Supported in part at URI by NSF and at GE by AFOSR.  bOn sabbatical leave from URI, now returned there.
Abstract: Magnetic properties of the ordered VPt3 alloy
Authors: Jesser R. , Kuentzler R.
Published: February 2003

The phase diagram of V-Pt1 presents several atomically ordered phases. The VPt3 alloy, which exists both in the disordered state and in the atomically ordered states with fcc Cu3Au-like [VPt3 (1)] and tetragonal TiAl3-like [VPt3 (2)] crystalline structures present unusual magnetic properties. The ordered VPt3 alloy is one of the very few alloys which are ferromagnetic, although both components are nonmagnetic. The magnetic properties have therefore been investigated in great detail in a large temperature range and in a large magnetic field range. The ferromagnetic properties for both ordered VPt3 alloys [TC = 240 K and μ0 = 0.101 μB per V atomgram for VPt3 (1) and TC = 210 K and μ0 = 0.075μB per V atomgram for VPt3 (2)] and paramagnetic properties for the disordered alloy have been reported.2 In this paper we present a detailed study of the critical behavior of VPt3 (1) and (2) around their Curie point in the frame of the scaling hypothesis. The magnetic critical exponents β, γ, and δ are obtained [β = 0.50, γ = 1.19, and δ = 3.380 for VPt3 (1) and β = 0.51, γ = 1.21, and δ = 3.373 for VPt3 (2)] and the critical magnetic Domb, Hunter, Widom equation of state is determined. The experimental results are very well reproduced.    1 R. M. Waterstrat, Metall. Trans. 4, 455 (1973).  2 R. Jesser, A. Bieber, and R. Kuentzler, J. Phys. (Paris) 42, 1157 (1981).
Ultrasound induced irreversible changes in the magnetization of highly magnetostrictive materials Tb0.27Dy0.73Fe2 and MnBi
Authors: Winter Calvin , Arrott A. S.
Published: February 2003

A sample, after being saturated in a high magnetic field, is in an unstable remanent state in a low or reversed magnetic field. Application of a burst of ultrasound at this point will result in an irreversible decrease in the remanent magnetization. By subsequently changing the magnetic field, and applying a second burst of ultrasound, a reduced irreversible decrease is effected. This observed behavior is a measure of the statistical correlation between the two magnetic states of the sample. We have successfully described this behavior with a modified Preisach model. We have observed irreversible changes in the magnetization of Tb0.27Dy0.73Fe2 (λ111 = 1.6×10−3) as large as 50% of the remanent magnetization, or 0.4% of the saturation magnetization, induced by ultrasound bursts of 107 dyne/cm2 at 20 °C. In MnBi (λs = −8×10−4) crystals in Bi, irreversible effects as large as 1.8% of the remanent magnetization, or 0.6% of the saturation magnetization, have been observed at 120 K.
Weak ferromagnetism and domain wall motion in a linear magnetic polymer
Authors: Scott J. C. , Zimm C. B. , Sarhangi A.
Published: February 2003

Susceptibility measurements from dc to 500 kHz have been made on the linear coordination polymer, poly(cobalt n-butylphosphinate). At high temperature the data conform to the classical Heisenberg antiferromagnetic chain with a mean field temperature of 28 K. Below about 20 K there is an excess susceptibility which saturates in modest fields. These results are described in terms of an antisymmetric exchange component which produces short-range weak ferromagnetic order in the paramagnetic phase. At still lower temperature the ac susceptibility shows a loss component, even in zero applied field, which we ascribe to the motion of domain walls in the weak ferromagnetization.
Temperature dependence of unidirectional anisotropy effects in the Permalloy-FeMn systems
Authors: Tsang C. , Lee Kenneth
Published: February 2003

We have systematically studied the temperature dependence of the exchange-induced unidirectional anisotropy field (HUA) for the Permalloy-FeMn system from room temperature up to ∼220 °C. Results show that HUA(T) decreases monotonically with T, vanishing around some critical temperature (Tc) which varies with sample configurations, film thicknesses, and deposition conditions, and in the best case is close to the Néel temperature of the bulk FeMn. The Permalloy/FeMn and the FeMn/Permalloy systems differ in their HUA(T) behavior, indicating a basic difference in the interface structures. Our results suggest a model where the interface comprises an ensemble of exchange paths, each with its own ordering temperature (To). The net HUA may then be regarded as an averaged behavior of all these To components. Using a special cooling procedure, we are able to study the distribution and behavior of these To components, with results showing that the FeMn/Permalloy system does exhibit a narrower and higher-valued distribution of To components. This result, together with the HUA(T) and Auger profile results, suggest that the FeMn/Permalloy system has a fundamentally sharper and more ideal interface than the Permalloy/FeMn system.
Magnetization and structure of Mn-Ni and Mn-Co layered magnetic thin films
Authors: Stearns Mary Beth
Published: February 2003

The large number of d-like conduction electrons in Mn causes the local moments of Mn to be aligned antiferromagnetically, whereas the smaller number of itinerant d electrons in Fe, Co, and Ni causes the d-conduction electron polarization (dCEP) to align these materials ferromagnetically. With the aim of altering the dCEP in a controlled manner, a series of thin films of total thickness of about 1.2 μ has been prepared by evaporating alternating layers of Ni and Mn or Co and Mn on highly polished oriented sapphire substrates. The layer thicknesses were varied between about 5 and 100 Å. Interference patterns from x-ray measurements indicate that the Ni-Mn films are layered with Ni(111) and predominantly β-Mn (221) layers. The Co-Mn films show predominantly hcp-Co (002) alignment and a Mn alignment which is similar to that of the Ni-Mn films. A wide variety of magnetic behavior is seen in these films, as expected due to the systematic variation of the dCEP across the films.
Magneto-optic properties of amorphous terbium-iron
Authors: Allen R. , Connell G. A. N.
Published: February 2003

The magneto-optic properties of rf sputtered amorphous TbxFe1−x(x≊0.21) alloys were investigated using reflectivity, ellipsometry, and polar Kerr measurements. Oxide growth in air at different temperatures was first studied, and the oxide composition and growth kinetics were correlated by ellipsometry and Auger measurements. Alloy films overcoated in situ with several thicknesses of SiO2 were then used for optical studies of the ’’unoxidized’’ interface, and the data obtained yielded the diagonal and off-diagonal elements of the dielectric tensor of unoxidized material.
Effects of crystalline precipitates on the soft magnetic properties of metallic glasses
Authors: Hasegawa R. , Ramanan V. R. V. , Fish G. E.
Published: February 2003

Effects of crystalline precipitates, nucleating at temperatures slightly below the crystallization temperatures, on the soft magnetic properties are reported for some selected metallic glasses. Emphasis is placed on the effects due to the difference of the crystalline symmetry of the precipitates. The glassy alloys selected for the present study are Fe85B15, Fe77B23, and Fe60Ni25B15, which tend to precipitate bcc-Fe, bct-Fe3B, and fcc Fe-Ni crystalline particles, respectively. It is concluded that the differences in structure of the precipitates are more important than their morphology in determining the ac properties of the materials at frequencies greater than 50 kHz.