Magnetic anisotropy and crystal structure of intermetallic compounds of the ThMn12structure

摘要

Intermetallic compounds of the type RE(TM1minus;xMx)12with RE=Y, Er; TM=Fe, Co; M=Si, Ti, V of the ThMn12tetragonal crystal structure have been studied by the singular point detection technique and highhyphen;resolution neutron powder diffraction in order to (a) evaluate both the rarehyphen;earth and transitionhyphen;metal sublattice contributions to the magnetocrystalline anisotropy, (b) compare the Fe and Co anisotropies in the ThMn12structure, and (c) to verify the existence of any preferential entrance in the transition metal sublattice for various stabilizing ions. The transition metal anisotropy is of the same type (Fe axial, Co planar) and magnitude as in RE2Fe14B compounds. However, there is no anomalous temperature behavior of the anisotropy fieldHa. With decreasing temperature, the value ofHaincreases from 21 kOe at 293 K to 37 kOe at 78 K in YFe11Ti. Similar values are obtained for other Fehyphen;based compounds. The contribution of Er to the anisotropy is found to be surprisingly low. The anisotropy field of ErFe11Ti varies from 24 kOe at 293 K to 63 kOe at 100 K. The observed low values of the Curie temperatures in these compounds appears once again to limit their use in possible applications. Neutron powder diffraction shows that the 8jand 8fsites of the ThMn12structure are virtually fully occupied by Fe, while the 8isite is partially occupied by Fe and V in YFe10V2.