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Research describing thermal expansion and perpendicular and parallel magnetostriction in a magnetic field is presented. In particular the magnetic properties of ferromagnetic martensites are investigated.

Mn, Co and Ni substituted Fe3.34Ge2 hexagonal germanides were investigated through structural, Mossbauer and magnetic studies. Fe was observed to enter exclusively 2a and 2d sites of the defective structure, while vacancies only occupy the 2d site in the congruent composition. The Ge atoms were found to be slightly displaced from 2c site of the B8(sub 2) structure towards an adjacent vacancy in a 2d site. Mn and Ni exclusively enter 2a and 2d site, respectively, while Co enters both sites with a preference for 2d.

The temperature behavior of the magnetization process and magnetic anisotropy in monoclinic Nd3(FeTi)29 and tetragonal Nd(FeTi)12 indicates that the temperature stimulated spin reorientation transitions characterize both the compounds. The first-order magnetization process, field-stimulated magnetization mechanism also characterizes the two compounds. The magnetization direction from the principal axes in both the compounds is determined by the resultant anisotropy of the Nd. The tetragonal C-axis is caused by Fe sublattice anisotropy.

The utilization of Zr6Co23-xMx (M=Fe,Ni and 0

The saturation magnetization, Curie temperature and magnetocrystalline anisotropy in rhombohedral and hexagonal Y-Co compounds were investigated. The results showed that the considered phases of the rhombohedrals and the hexagonals were all derived from the hexagonal CaCu5 unit. The magnetic characteristics in the compounds were associated with the cobalt content. The Co sublattice anisotropy varied linearly with the Co content in the phases.

The singular point detection technique was used to study competing anisotropies and magnetization processes in the pseudoternary (HoxEr1-x)Fe10V2 tetragonal system. Results showed that competition among the anisotropy of the magnetic sublattices produced a spin reorientation transition axis to cone in erbium containing samples when the temperature decreased.

Thermomagnetic and magnetocaloric (MC) properties of Ni2MnGa Heusler alloys are found to be very sensitive to small composition variations. It is shown that the temperature behavior of ac susceptibility mimics that of MC properties of the samples. The coincidence of magnetic and structural transformations is found for a Mn-rich composition. As in the case of Ni-rich alloys, the magnetocaloric effect is enhanced at the transitions co-occurrence. The increase of Mn content, with respect to the stoichiometric value, rapidly decreases anisotropy field and saturation magnetization. [ABSTRACT FROM AUTHOR]

The temperature dependence of the magnetocrystalline anisotropy and the effects of pressure on the intrinsic magnetic properties of the hexagonal DO19 phase of Fe3Ge single crystals have been studied. The easy-magnetization direction is in the basal plane at low temperatures and a spin reorientation transition from plane to axis occurs at 377 K, with increasing temperature. The thermal dependence of the magnetic anisotropy of Fe3Ge has been determined and described in the frame of the Carr model for localized moments. The partial substitution of Fe by Mn, besides reducing both the saturation magnetization and Curie temperature, extends the axial region widely. Pressure has little influence on the magnetic moment but it markedly affects the crystalline anisotropy. The planar character of the anisotropy is indeed reduced in both pure and substituted compounds. The application of high pressure, the partial substitution of Fe by Mn and the increase of temperature have similar effects on the magnetocrystalline anisotropy of Fe3Ge—all induce a reduction of its planar character, favoring a plane to axis spin reorientation transition. [ABSTRACT FROM AUTHOR]

Magnetometric and magnetic force microscopy (MFM) measurements were performed on [Co(6 Å)/Au(27 Å)][SUB27] multilayers grown at different sputtering pressures (0.8-9 Pa). All the as-prepared samples display perpendicular magnetic anisotropy that has its maximum value at intermediate pressures, while a monotonic decrease of the saturation magnetization was found with increasing pressure. As found by MFM, a relevant characteristic of these systems is the magnetic stripe domain structure. The application of the stripe domain model of Draaisma and de Jonge [H. J. G. Draaisma and W. J. M. de Jonge, J. Appl. Phys. 62, 3318 (1987)] allows us to satisfactorily reproduce the magnetization processes and to determine the anisotropy constants (K[SUBeff]) starting from the domain width. The obtained K[SUBeff] values display the same behavior and order of magnitude as those deduced from the area enclosed between parallel and perpendicular magnetization curves. The measurement of the stripe domain size with MFM thus results in an easy and reliable method for the evaluation of the anisotropy constants in multilayers with perpendicular anisotropy. [ABSTRACT FROM AUTHOR]

Linear thermal expansion and magnetostriction measurements under a magnetic field up to 20 kOe, applied parallel and perpendicular to the measuring direction and in the temperature range of 10-300 K, have been performed on a Ni[sub 2]MnGa polycrystal. The effects of zero-field cooling and field cooling on both the self-strain (H=0) and the magnetic-field-induced strain (MFIS) have been studied. We have found that the MFIS strongly depends on whether a magnetic field was applied during the cooling process. The applied magnetic field facilitates the growth of specific orientation variants along the field direction as the sample is cooled down through martensitic transformation. However, the application of a field in the martensitic phase induces a negligible motion of twin boundaries. On this basis, the singular point detection technique performed on polycrystalline specimens results in being the easiest and most direct way by which to determine the anisotropy field in this class of materials. The temperature behavior of the anisotropy constant and field has been determined for Ni[sub 2]MnGa. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Powder neutron diffraction at 1.5K has been used to investigate the crystal and magnetic structure, whilst the Singular Point Detection (SPD) technique has been used to measure the temperature and composition dependence of the magnetic anisotropy of [Fe.sub.60][Ga.sub.40-x][As.sub.x] (x = 6, 23) and Fe[Ga.sub.23][Sb.sub.17]. The compounds [Fe.sub.60][Ga.sub.17][As.sub.23] and Fe[Ga.sub.23][Sb.sub.17] are isotypic with [Ni.sub.2]In ([P.sub.63]/mmc) and [Fe.sub.60][Ga.sub.34][As.sub.6] is a complex modification of this with a doubling of the lattice constant a of the parent [Ni.sub.2]In subcell. The neutron data show that the magnetic structures are planar at 1.5K. Analysis of the SPD signals also indicates a planar anisotropy for all compositions at low temperatures. The temperature dependence of the anisotropy field [H.sub.A] is very similar for the Ga compounds whilst for the Sb compound a smoother dependence is observed at low temperatures. The anisotropy field increases irrespective of As or Sb substitution. The Curie point, saturation magnetization and anisotropy field can be simultaneously increased by changing the relative content of non-magnetic ions.

This report presents the results of a European intercomparison of measurements on permanent magnetic materials. The intercomparison consisted of two parts, namely (A) measurements on cylindrical specimens of AlNiCo and NdFeB in a closed magnetic circuit; (B) measurements on spherical specimens of NdFeB in an open magnetic circuit using vibrating sample or SQUID magnetometers. A total of 24 laboratories took part in the intercomparisons. Together with the other specimens, nickel reference specimens were circulated for calibration purposes. The results of the intercomparisons are complex, but in general the agreement obtained was quite good. A comparison of the two parts shows that the difference B(sub r) is relatively small, whereas the differences in H(sub c), H(sub cB) and (B center dot H)(sub max) are considerable, which can be interpreted in the light of the aging of the NdFeB spherical specimens due to the preparation process.

The magnetothermal and magnetocaloric (MC) properties of Mn-rich compounds in the vicinity of the co-occurrence of magnetic and structural transitions are investigated. It is demonstrated that the temperature behavior of ac susceptibility mimics that of MC properties of the samples and that the magnetocaloric effect is enhanced at the transitions co-occurrence.

The magnetocrystalline anisotropy of the Fe in the hexagonal phase of the Fe3Ge semi metallic compound is reported and the origin of the plane to axis spin-reorientation transition (SRT), which occurs without competing anisotropy contributions in this single-magnetic-site system is discussed.

Carries out a systematic study of the magnetic properties of the system Y[sub1-x]Pr[subx]Co[sub5] to clarify the role of 3d and 4f anisotropy in the occurrence of first-order magnetization processes and spin reorientation transitions in PrCo[sub5]. Information on spin reorientation transition temperatures; Presence of high-order terms in anisotropy energy expansion; Existence of competing anisotropies and consequent existence of effective anisotropy constants.

Presents information on a study which measured the reversible transverse susceptibility X[sub 1] of a ferromagnet having a positive uniaxial anisotropy as a function of the applied magnetic field. Methodology of the study; Results and discussion.

Presents a study of the magnetocrystalline anisotropy of manganese aluminum and manganese aluminum carbon alloys. Anisotropy field value; Factor attributed to the observed changes in the magnetization curve shape and in coercivity; Comparison between the magnetization curve of isotropic polycrystal with the computed magnetization curve of a random polycrystal.

Analyzes carbon monoxide, maganese and nickle substituted Fe3.34Ge2 hexagonal germanides to perform tructural (x-ray and neutron diffraction), Mossbauer, and magnetic investigations. Methodology used to conduct the study; Information on single crystal x-ray diffraction; Details on the neutron powder diffraction; Findings of the study.

Presents a study which investigated the influence of vanadium on the magnetic anisotropy of iron and rare earth (RE) sublattices and on the magnetic phase diagram of these systems. Magnetic properties of the vanadium content of the compounds; REFe[sub12-x] V[subx] (RE= erbium, terbium, yttrium); Variation of the spin reorientation transition temperature; Composition dependence of the Curie temperature.

Presents information on a study which examined the magnetic anisotropy and crystal structure of intermetallic compounds of the thorium manganese[sub12] structure using singular point detection technique and high resolution neutron powder diffraction. Advantage of the neutron diffraction technique; Structure determination; Variation of the iron sublattice anisotropy.

Presents a study which investigated the crystal and magnetic structure of gallium substituted manganese aluminum alloys by neutron diffraction. Experimental method used; Measurement of the saturation magnetization and the anisotropy field; Influence of gallium substitution on the magnetic and structural properties.

Studies the first-order field-induced magnetization transitions in single crystals. Details on the experiments; Results of the study; Conclusion.

Presents a systematic study of the effects of cobalt substitution on the crystal structure and magnetic anisotropy of Y[sub2]Fe[sub14-x]Co[subx]B and Nd[sub2] Fe[sub14-x] Co[subx]B to clarify the different roles and contributions to the anisotropy of both rare earth and transition metals. Preparation of the polycrystalline samples; Measurement of the effects of cobalt substitution on the tetragonal unit cell parameters.

Presents information on a study which investigated induced magnetic anisotropy and spontaneous distortion of the structure both in powdered and bulk intermetallic samarium compounds. Methods; Results; Discussion.