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We have carried out neutron and magnetic studies on [Nd.sub.2][Fe.sub.17-x][T.sub.x] (T=Si, Mn) alloys. The unit cell of the compounds contracts with both Si and Mn substitution. Si atoms avoid the 6c site, prefer the 18h site strongly, fill the 9d site steadily and fill the 18f site only at relatively high Si concentration. Mn atoms avoid the 9d sites but prefer the 6c site strongly, while the 18f site and 18h site fill slowly. The Si site occupancies appear to be dominated by the crystal environment while the Mn site occupancies are dominated by steric considerations. The Curie temperature of the compound [Nd.sub.2][Fe.sub.17] increases significantly with Si substitution but is only affected slightly by the Mn substitution. Although the unit cell contracts with increasing Si concentration, the average length of bonds to the Fe(6c) and the Fe(18f) sites increase slightly at x

The determination of unit-cell dimensions and magnetic characteristics of R(sub 2)Fe(sub 17)-type alloys reveal that Curie temperature and the saturation magnetization of alloys can be enhanced by the replacement of Fe by Co. The Curie temperature enhancement indicates an increase in the strengthening of average 3d-3d exchange reactions.

The crystal structure and magnetic characteristics of ternary compounds based on R2Fe14Si2 were investigated using x-ray diffraction analysis. The results showed that the sample compounds crystallized in the rhombohedral Th2Zn17-type structure when R was Nd or Gd and in the hexagonal structure when R was Y, Dy, Ho or Er. The Curie temperature behavior followed the root of the de Gennes function.

To understand the effects of nucleation fields and intergranular dipolar interactions on the magnetization reversal mechanism, recoil curves from the major hysteresis loop have been measured on a sample of sintered PrFeB as a function of temperature from 150 to 300 K. At room temperature the reversible magnetization behavior indicates a reversal mechanism of nucleation of domain walls whose motion after nucleation is resisted by dipolar fields. As the temperature is reduced, the coercivity, and hence the nucleation field, is observed to increase while the dipolar fields, dependent on microstructure and saturation magnetization, remain approximately constant. These temperature-dependent changes in the relative magnitudes of the dipolar field and nucleation field cause the reversible magnetization behavior to change from domain wall motion to rotation. This change in behavior is attributed to the supposition that at temperatures where the nucleation field exceeds the dipolar field, once nucleated, domain walls are swept out of the material. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Deals with a study which determined the magnetic characteristics and unit-cell dimensions of the R[sub2]Fe[sub17] silicides. Background to the study; Experimental details; Results and discussion.

Investigates the crystal structure and magnetic properties of ternary compounds based on R[sub2]Fe[sub14]Si[sub2]. Measurements of lattice parameter; Curie temperature of the compounds; Saturation magnetization.

Presents a study that examined the composition and magnetic field dependence of the spin-reorientation behavior in a quaternary alloy system. Methodology; Analysis of the temperature dependence of magnetization in the quaternary alloy; Evaluation of the thermal hysteresis of the quaternary alloy.

Presents a study which investigated the structural and intrinsic magnetic characteristics of Tm[sub2-x]Dy[subx]Fe[sub14]B and Tm[sub2]Fe[sub14-x]Co[subx]B. Studies on the effect of the addition of cobalt element in improving the intrinsic magnetic properties in R[sub2]Fe[sub14]B systems; Structural and magnetic data of single-phase materials of Tm[sub2]Fe[sub14-x]Co[subx]B; Results of x-ray diffraction in the Tm[sub2-x]Dy[subx]Fe[sub14]B systems.

Reports on the magnetic phase diagram of (Tm[subx]Dy[sub1-x])[sub2]Fe[sub14]B and other mixed rare-earth systems. Parameters employed in the calculation of magnetic phase diagrams; Information on the shape of the plane-cone boundary.

Discusses the employment of measurements of lattice parameters and bulk magnetization on quaternary compounds and their hydrides. Purities of starting metals; Direction of magnetization of the host compounds.

Provides a quantitative evidence of a ferromagnetic iron-rich minor phase present in both melt-quenched/die-upset and sintered magnets based on the Nd[sub2]Fe[psub14]B composition. Determination of hysteresis loops; Saturation magnetization of the minor phase; Paramagnetic slope of the major phase; Calculated volume of the impurity phase in the die-upset magnets.

Presents information on a study which analyzed the basic magnetic features for LaCo[sub13]-based systems in which cobalt has been replaced by iron (Fe), aluminum (Al) or Fe and Al and also systems in which lanthanum has been partially replaced by neodymium. Preparation of specimens by an induction melting under a highly pure argon atmosphere; Composition dependence of the magnetic moments of La(Co[sub1-x]Al[subx])[sub13] compounds; Illustration of the qualitative band scheme.