STRUCTURE SENSITIVITY OF MAGNETIZATION PROCESSES AT THE SPIN-REORIENTATION TRANSITION IN ND2FE14B

Calculations based on different micromagnetic models were carried out in order to describe the behavior of the ac susceptibility in the temperature range of the spin-reorientation transitions in hard magnets. It was found that the rotational susceptibility shows a sharp cusp at the transition temperature, while the contribution due to an increase in the domain-wall mobility is less significant. As well, there is a significant contribution of domain-wall processes to the overall susceptibility over the entire range of temperatures studied (80-180 K). For randomly oriented bulk samples, the susceptibility cusp has been experimentally observed. The susceptibility of randomly oriented powders shows only a moderate temperature dependence below the transition, followed by a sharp decrease at the transition temperature. The frequency dependence of the susceptibility showed the behavior expected for conducting samples, proving that domain-wall dynamics (e.g., aftereffects, lattice-defect-domain-wall interactions, etc.) do not play a role in the observed temperature dependence of the susceptibility.