Magnetic and crystallographic properties of NdCo4M (M=B, Al, and Ga)

Abstract
The magnetic and crystallographic properties have been investigated for NdCo4M (M=B, Al, and Ga). The temperature dependencies of lattice parameters have been determined between 80 and 730 K by x‐ray diffraction. NdCo4B crystallizes in the CeCo4B‐type structure, whereas NdCo4M (M=Al and Ga) exhibits a CaCu5‐type structure. Magnetic properties of NdCo4B show a clear difference from those of its Al and Ga counterparts. All these compounds exhibit planar anisotropy in the low‐temperature regime, and the spin‐reorientation temperature is found to be ∼280 K for NdCo4Al and NdCo4Ga, whereas NdCo4B is planar up to its Curie temperature. Thermal expansion curves of c axes show an anomalous contraction for NdCo4B and expansion for NdCo4Al and NdCo4Ga only in the temperature region of planar anisotropy.