Structure and magnetic properties of RCo7-xZrx (R=Y, Gd, Nd, or Ho, x=0-0.8)

Alloys with the composition RCo7-xZrx (R=Y, Gd, Nd, or Ho, x=0-0.8) were sy nthesized and characterized in the temperature range from 10 to 1273 K and in fields up to 5 T. As with the R=Sm, Pr, or Er systems studied earlier in our laboratory, the effects of Zr doping on the stability of TbCu7 structu re phase and changes in the magnetocrystalline anisotropy H-A are observed in the systems in which the rare earth is Y, Gd, Nd, or Ho. Nearly single p hase TbCu7 structure materials were formed in the as-cast alloys when x=0.1 and 0.2. In the case of R=Y or Gd, a large increase in H-A (which is mainl y contributed by Co sublattice) by Zr doping was observed. For R=Y, H-A inc reases from 18 kOe for x=0 to 74 kOe for x=0.2 at 300 K and from 20 kOe for x=0 to 82 kOe for x=0.2 at 10 K. For R=Gd, H-A increases from 35 kOe for x =0 to 140 kOe for x=0.2 at 300 K and to 182 kOe for x=0.2 at 10 K. In the c ase of R=Ho and Nd, the R-sublattice favors a planar anisotropy at room tem perature, presumably due to the negative second order Stevens' coefficient. For R=Ho, the anisotropy changes from planar for x=0 to axial with H(A)sim ilar to 60-70 kOe at 300 K when x=0.1 and 0.2. For R=Nd, H-A is dominated b y R sublattice which results in a planar anisotropy. Other magnetic propert ies such as magnetization, Curie temperature, and spin reorientation temper ature for these alloys are presented. (C) 2000 American Institute of Physic s. [S0021-8979(00)21508-9].