First-order magnetization process in Nd(Fe,M) 12Z y (M=Mo, Ti, V, Z=C, N)

Abstract

The magnetic properties of textured samples of Nd(Fe,M) 12Z y (M=Mo, Ti, V, Z=C, N) with ThMn 12-type structure have been investigated using a superconducting solenoid with fields up to 16 T and a pulsed-field solenoid with fields up to 40 T. A field-induced transition in the magnetization curves of the carbide samples was detected for fields applied perpendicular to the alignment direction. This transition was identified as a first-order magnetization process (FOMP). The FOMPs depend on carbon concentration, temperature and the type of M element. They appear at a certain carbon concentration and at temperatures below 150–100 K. The FOMP field of NdFe 10.5Mo 1.5C y is much higher than that of NdFe 10.5V 1.5C and NdFe 11TiC y . Transitions found in the DC magnetization measurements up to 16 T on the carburized samples could be confirmed by the pulse-field measurements. Contrary to theoretical suggestions, no FOMP could be found in the nitrides for fields up to 40 T. The temperature dependence of the FOMPs is due to the thermal evolution of the anisotropy constants K i ( i=1, 2, 3 ) of the carbides related to the corresponding crystalline-electric-field (CEF) parameters.