DESCRIPTION OF MAGNETIC-ANISOTROPY AND SPIN-REORIENTATION TRANSITIONSIN 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-reorie ntation transitions. The temperature dependence of the magnetic anisot ropy field was determined by means of the singular-point-detection tec hnique 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. Fitti ng the experimental data, a set of crystal-field and exchange-field pa rameters for Nd3+ ions was deduced. A first-order spin-reorientation t ransition from uniaxial to conical phase and a type-2 first-order magn etization process in the perpendicular field are calculated for NdFe11 Mo. A canted magnetic structure and a type-1 first-order magnetization process in the axial field are predicted for NdFe12-xMoxN. A change o f rare-earth anisotropy after nitrogenation was explained by a bonding charge and a superposition model. The calculated temperature dependen ce of the anisotropy fields in NdFe12-xMoxN is in good agreement with the experimental data over a wide temperature range. (C) 1996 American Institute of Physics.