Magnetic Characteristics of RCo7−xZrx Alloys (invited) (R = Sm, Pr, Er, Gd, and Y)

ABSTRACTA brief review is presented of recent work dealing with the structure and magnetic properties of RCo7−x Zrx alloys (R=Sm, Pr, Er, Gd, and Y). The experimental results obtained are consistent with a model in which Zr atoms partly replace dumbbell Co atoms and play an important role in stabilizing the TbCu7 structure while significantly increasing the anisotropy field (HA). For example, when R=Sm, HA increases from 90 kOe for x=O to 130 kOe for x=0.2 at 300 K, and from 140 kOe for x=0 to 220 kOe for x=0.2 at 10 K. In the case of R=Y and Gd, HA is mainly contributed by the Co sublattice. For R=Y alloys, HA increases 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 alloys, HA shows the largest enhancement. It increases from 35 kOe for x=0 to 140 kOe for x=0.2 at 300 K and from planar for x=0 to uniaxial with 182 kOe for x=0.2 at 10 K. In general, experimental results are in accord with the theory of Greedan and Rao for anisotropies of R-Co alloys. The magnetic moments for cobalt and rare earth in RCo7−xrx compounds (x=0∼A).2) have been estimated from the experimental values. The results show that they are nearly the same as those in RCo5 or R2Co17. The Co moment is 1.5∼;1.6 μB. Some phase transition phenomenon between RCo5, RCo7, R2Co17and R2Co7at different heat treatment conditions will also be discussed.