摘要:

The dependence of the crystal structure and magnetic properties of iron films on preparation conditions has been investigated in detail by using a double‐ion‐beam sputtering system. During sputtering of an iron target by argon ions, the growing surfaces of iron films were bombarded by nitrogen or hydrogen ions with different kinetic energies below 500 eV. It has been found that these ions changed significantly the film structure and magnetic properties through the process of collision and reaction with iron atoms at the surface layer of growing film. As a result, the small amount of hydrogen or nitrogen added into iron films by ion bombardment improved effectively the soft magnetic properties of iron films. The iron films with saturation magnetization 4&pgr;Msas large as 22 kG and coercive forceHcas low as about 5 Oe were prepared by adjusting the accelerating voltage in the range of 100–300 V and the partial pressure of hydrogen or nitrogen in the range of 10−4–10−5Torr.

ISSN:0021-8979    

DOI:10.1063/1.340211

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We have implanted boron ions into films of Fe‐Ni alloy composition. A homogeneous distribution of boron was determined from the sputter Auger analysis with a concentration of 18% and 34% for low‐ and high‐dose implantation, respectively. The resistivity of film was increased by a factor of 2 and 4 as a result of low‐ and high‐dose implantation, respectively. The magnetic properties of these films are studied as a function of annealing temperature by using FMR measurements. Both the uniaxial anisotropy field and FMR linewidth are dramatically decreased as a result of annealing at elevated temperatures. The changes of effective magnetization of these films are strongly dependent on implanted boron concentration.

ISSN:0021-8979    

DOI:10.1063/1.340212

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We have produced Fex‐Ni80−x‐B15‐Si5(x=20, 40, and 75) and permalloy thin films on a silicon substrate using ion‐beam sputtering technique. Four‐point probe measurement indicated that quarternary films had 3–4 times higher resistivity than permalloy films, and this ratio was not changed after thermal annealing. The values of saturation magnetization were determined to be 5–13 kG depending on Fe concentration. The anisotropy fields of these films were in the ranges of 2–15 Oe after deposition, however, these values were reduced by more than 50% after annealing with field. The lowest value of the anisotropy field was 1.3 Oe for the permalloy film after thermal annealing without field.

ISSN:0021-8979    

DOI:10.1063/1.340213

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The in‐plane uniaxial anisotropyKu, induced by a magnetic field applied during the deposition, was investigated in amorphous thin films of Co1−xZrxand Co1−x−yZrxMy(M=Ti, Nb, and Pt) obtained by rf sputtering. For a given concentrationKupresents a bell‐shaped variation as a function of Ar pressurePAr. The critical pressure for which the maximum value ofKuis obtained and the absolute value of (Ku)maxchanges for the various alloys. These results and the high value of (Ku)maxare explained by a model where (Ku)maxis related to the local anisotropy via the local structure upon the nonmagnetic metal. (Ku)minis essentially related to a pseudodipolar short‐range order.

ISSN:0021-8979    

DOI:10.1063/1.340214

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Perturbations to the Stoner–Wohlfarth threshold in 2×20 &mgr;mM‐Rmemory elements have been examined experimentally and analytically. For the small dimensioned elements studied the perturbations are large. The thresholds were reduced up to 50% for transverse elements and increased 10% or more for longitudinal elements.

ISSN:0021-8979    

DOI:10.1063/1.340215

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The proposal of an interaction potential between 180° Bloch walls and nonmagnetic obstacles, precipitates or pores, is presented. Use is made of the analogy between this phenomenon and the pinning of grain boundaries in polycrystalline materials. The model takes into account the increase of energy due to the flexibility of the boundary and it is applicable to low magnetization materials. Using this approach it is possible to calculate the coercive force and to compare it with early findings. The numerical values obtained are in agreement with the values we find in the literature with the advantage that the proposed potential is expressed in a simple analytical form.

ISSN:0021-8979    

DOI:10.1063/1.340189

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The behavior of a parallel array of stripe domains subjected to a periodic field was studied. Experiments were performed on a layer of single‐crystal ferrimagnetic garnet (bubble material) featuring in zero field a periodic pattern of parallel stripe domains. The layer was applied to a magnetic tape on which a sinusoidal waveform was recorded. The garnet‐tape distance, and hence the interaction strength, could be varied. The resulting domain patterns were observed in polarized light. We present results obtained for a recorded wavelength (66 &mgr;m) equal to six times the natural domain period (11 &mgr;m). The domain structure adapted itself by reducing the number of stripes, in particular by means of dislocation glide in the stripe array. This resulted in various modulated stripe patterns. The transitions between structures with different stripe numbers could be observed. These were achieved by local distortions of the parallel array around dislocations. The total energy of the garnet layer was calculated as the sum of magnetostatic, wall, and interaction energies for various interaction strengths. The equilibrium domain configuration could be deduced by minimizing the energy with respect to wall positions. The calculated modulated domain structures are in agreement with the observed one.

ISSN:0021-8979    

DOI:10.1063/1.340190

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A method for constructing three‐dimensional solenoidal magnetization distributions, with invariant magnitude ofm, in arbitrarily shaped objects is presented. The formalism harks back to the theory developed by van den Berg for two‐dimensionalmdistributions. The space within a general object &OHgr; is partitioned intoisubspaces &OHgr;i, described by a family of surfaces to which the magnetization is tangent. A characteristic equation which defines the course ofmat each of the surfaces is derived. A boundary condition formarises naturally, or can be chosen to determinemat the surface. Within the above framework an infinite number of solutions are generated that, in general, exhibit singularities. Special attention, also from the topological point of view, is paid to themdistributions having point defects only.

ISSN:0021-8979    

DOI:10.1063/1.340191

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

In this paper, we will analyze the changes in the kinetics of the induced anisotropy due to preannealing in 300‐A˚ and 1‐&mgr;m‐thick Co94Zr6amorphous films. Samples were prepared by a dc sputtering method. A silicon wafer with SiO2overcoat was used as a substrate material, and a field of 200 Oe was applied during the deposition to induce uniaxial anisotropy. Based on x‐ray data and resistivity measurements, the films were considered amorphous. The samples were annealed in a magnetic field at temperatures up to 500 °C, and the annealing time was varied from 0.5 to 400 h. As previously reported, the anisotropy,Ku, in as‐deposited samples is a function of sample thickness and varied from 1.6×104ergs/cm3for 300‐A˚ film to ∼1×104ergs/cm3for 1‐&mgr;m films [T. Jagielinski, J. Appl. Phys.61, 3237 (1987)]. It was found that theKuin thick films is reversible, and the kinetics can be fully explained by the anelasticity model [T. Egami, Rep. Prog. Phys.47, 1601 (1984)]. The mean value of the activation energy is ∼2 eV for samples preanneled at 375 °C. However, in the case of thin films, an additional irreversible component of anisotropy, always along the direction of the field applied during the deposition, is observed. The magnitude is a growing function of annealing temperature, and is as large as 3×104ergs/cm3for a 300‐A˚ sample preanneled at 400 °C. The origin of the irreversible component of the anisotropy is not well understood. Based on x‐ray data, we concluded that this effect is not related to crystallization. However, since anisotropy is thickness dependent, the structure of the film‐substrate interface seems to be responsible for the irreversible part. The reversible parts of anisotoropy behave similarly in both thin and thick films and are 1.6×104ergs/cm3and 8×103ergs/cm3for 300‐A˚ and 1‐&mgr;m films, respectively.

ISSN:0021-8979    

DOI:10.1063/1.340192

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report on the dc susceptibility of the insulating spin glass Rb2Cu1−xCoxF4, withx=0.22. This model compound is a realization of the two‐dimensional short‐range Edwards–Anderson model, which has competing nearest‐neighbor Ising interactions. Below a frequency‐dependent freezing temperature spin‐glass behavior is observed for longitudinal spin components only. The nonlinear part of the susceptibility is found to excellently obey staticTc=0 scaling with &bgr;=0.0±0.1 and &Dgr;=3.2±0.2, in conformity with the Monte Carlo results for the two‐dimensional Edwards–Anderson model,Tc=0, &bgr;=0, and &Dgr;=3.5±0.5. These findings thus provide experimental evidence for the lower critical dimensionality for Ising spin glasses to exceed 2.

ISSN:0021-8979    

DOI:10.1063/1.340193

出版商:AIP    

年代:1988

数据来源: AIP