Description of magnetic anisotropy and spin–reorientation transitions in NdFe12−xMox and NdFe12−xMoxN (x=1.0, 2.0, 3.0)

NdFe12−xMox and NdFe12−xMoxN (x=1,2,3) were investigated by studying the anisotropy field and the temperature or field‐induced spin–reorientation transitions. The temperature dependence of the magnetic anisotropy field was determined by means of the singular‐point‐detection technique for polycrystalline aligned samples. A theoretical explanation of the magnetic anisotropy and the magnetic phase transitions is given. The temperature dependencies of the rare‐earth anisotropy constants were calculated using the single‐ion model within linear theory. Fitting the experimental data, a set of crystal‐field and exchange‐field parameters for Nd3+ ions was deduced. A first‐order spin–reorientation transition from uniaxial to conical phase and a type‐2 first‐order magnetization process in the perpendicular field are calculated for NdFe11Mo. A canted magnetic structure and a type‐1 first‐order magnetization process in the axial field are predicted for NdFe12−xMoxN. A change of rare‐earth anisotropy after nitrogenatio...