Peculiarities of the magnetocaloric effect in FeRh-based alloys in the vicinity of the first order magnetic phase transition

Abstract

Medical applications of magnetocaloric effect (MCE) require possibility for precision shift of a temperature of the magnetic phase transition at the same MCE value and minimize irreversibility. Thus, detail dynamic MCE investigation of such alloys with non-toxic biocompatible dopants need to be done. In present work, the giant magnetocaloric effect, which is observed in the whole family of Fe-Rh alloys, has been investigated in Pd-doped samples in slowly cycled magnetic fields of up to 1.8 T in magnitude for a range of temperatures, 250 K < T < 350 K. The shift of the ferromagnetic/antiferromagnetic transition temperature down towards room temperature and the decrease in the MCE have been observed in these alloys in comparison with a quasi-equiatomic FeRh alloy. The measurements have also shown an asymmetric behaviour of the first order magnetic phase transition with respect to whether the transition is traversed by heating from lower temperatures or cooling from above. These peculiarities have been explained in the framework of the ab-initio density functional theory-based disordered local moment theory of the MCE. The results have been compared with the those for the non-doped FeRh alloy. Thus features of the first order magnetic phase transition that these alloys have in common have been revealed which enable some predictions to be made appropriate for practical applications.

Peculiarities of the phase transformation dynamics in bulk FeRh based alloys from magnetic and structural measurements

“…Magnetization and magnetocaloric effect were measured in our previous works [34,35] using the same samples. Magnetization measurements were performed using a vibrating sample magnetometer (VSM, Toei Co Ltd. model-5) with a sweep rate of 1 K/min.…”

“…Therefore, this has sometimes led to a lack of necessary experimental data on the samples, such as precise composition and phase fraction: crucial in the case of FeRh. Here we complete thorough studies on our samples, for which the results of structural, magnetic, and magnetocaloric experiments have been published [34,35].…”