Effect of Dy substitution on the magnetocrystalline anisotropy of GdCo4B

Abstract

X-ray diffraction and magnetization measurements have been performed for powdered and field-oriented samples of Gd1−xDyxCo4B with x=0, 0.05, 0.1, and 0.2. It has been found that Gd1−xDyxCo4B with x=0.2 has a planar magnetic anisotropy in the temperature region below room temperature; however, the samples with x=0.05 and x=0.1 have an axial magnetic anisotropy at room temperature and transform to a tilted state in the low-temperature region. By analyzing magnetization curves measured in a pulsed field up to 140 kOe at T=4 K and also in a static field up to 12 kOe at 78 K for the field-oriented samples with x=0.05 and x=0.1, approximate values of magnetic anisotropy constants of a Dy ion in Gd1−xDyxCo4B, K1(Dy) and K2(Dy), have been determined to be −2.1×10−14 erg/Dy and 1.3×10−14 erg/Dy, respectively. By comparing these values with those of DyCo5.2, it is found that K2(Dy) in the CeCo4B-type structure is enhanced in one order by the crystallographic change from the CaCu5- to the CeCo4B-type structure.