Intrinsic and Extrinsic Magnetic Properties of Rare Earth-Transition Metal-Metalloid Alloys

Abstract

Several groups of rare earth-iron-boron or transition metal alloys have been examined by various experimental techniques with the aim to understand the magnetic properties at the atomic level and relate them to the macroscopic magnetic properties. Investigations of substituted R₂Fe_14-xCo_xB alloys (R=Y,Dy; x=0,l,2) have shown that Co enters preferentially in the c or k₂ site of the R₂Fe₁₄B structure. The change of the easy direction of magnetization from the plane to the c axis has been studied in a series of pseudoternary alloys of the type Er_2-xDy_xFe₁₄B with 0 < x < 1.5. Within the R-Fe-B system the compounds of the type R_1+eFe₄B₄ and RFe₄B were also investigated. The first group forms across the whole lanthanide series. Magnetic ordering occurs at temperatures between 4.2 and 25 K for R=Pr, Nd, Sm, Gd, Tb, Dy, Ho. The RFe₄B compounds (R=Er,Tm) have axial anisotropy. The distribution of Fe and B in the i and (c,d) sites of the hexagonal P6/mmm structure was investigated by Moessbauer and X-ray measurements. A series of new alloys of the pseudobinary type RFe_12-xT_x (R=Gd, Nd; T=Ti, V, Cr, Mo) crystallizing in the ThMn₁₂ structure has been prepared. They show axial anisotropy and anisotropy fields H_A≅3 kA/m. A two phase system prepared by annealing melt spun samples with composition R₂Fe₇B₃ was found to possess high coercivities at room temperature.