Co energy and magnetization anisotropies in RCo5 intermetallics between 4.2 K and 300 K

The magnetocrystalline anisotropy has been known for a long time to be very large in the RCo5 intermetallics. The recent availability of high D.C. magnetic fields up to 200 kOe has enabled us to carry out an extensive experimental study of the energy and magnetization anisotropies in YCo5 from 4.2 K to 300 K. The magnetization anisotropy reaches 4% at 4.2 K. From a polarized neutron study on NdCo5 we find that this anisotropy of magnetization originates mainly from the 2c site. Previous measurements on YCo5 had shown that the orbital contribution to the 2c moment is large. Hence, we conclude that the Co magnetization anisotropy in RCo5 comes from a large orbital contribution to the magnetic moment. Finally, we account for the observed discontinuity in the magnetization at its reorientation in RCo5 ferrimagnets, and for the absence of a similar discontinuity in NdCo5 which is a ferromagnet.