Magnetic properties of RCo4M (R=Y, Nd and Ho; M=B, Al and Ga)

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Abstract
Magnetic and crystallographic measurements have been made for the compounds RCo4M (R=Y, Nd, and Ho; M=B, Al, and Ga) to intercompare the magnetic properties of RCo4B, RCo4M (M=Al and Ga) and RCo5. The compounds RCo4B crystallize in the CeCo4B type structure, while RCo4M (M=Al and Ga) in the CaCu5 type. The following main conclusions have been obtained: (1) the Curie temperature and the averaged Co-moment of RCo4M (R=Y, Nd, and Ho; M=B, Al, and Ga) are lower and smaller than those of RCo5, respectively, and 6i-site Co-moment in RCo4B is smaller than the 2c-site Co-moment by the influence of the neighboring B-layer; (2) magnetocrystalline anisotropy of R-sublattice of RCo4B is stronger than that of RCo5, while that of RCo4Al is remarkably weaker than that of RCo5; (3) the Co-sublattice anisotropy constants of YCo4M (M=B and Al) are 20% or less of that of YCo5; and (4) JR-Co and JCo-Co, which are the exchange parameters of the atomic pairs in NdCo4M (M=B and Al), have been estimated to be JR-Co/k ≂ 7 K and JCo-Co/k ≂ 200 K, where k is the Boltzman constant.