Multifunctional properties of Cr-substituted ferromagnetic Nd2Fe17

Abstract

The detailed X-ray diffraction studies of the structural phase along with its thermal expansion properties have been carried out of the rare-earth based compounds Nd2Fe17-xCrx (x = 0, 0.5, 1.0, and 2.0). They are crystallized in the rhombohedral structure (Th2Zn17 type) with space group R-3m. A very negligible (close to zero) thermal expansion coefficient |α| = 1.9 × 10−6 K−1, was found over a large temperature range 15–320 K in Nd2Fe16.5Cr0.5 compound (TC ~ 366 K) attributable to the diminution of magneto-volume effect. This kind of zero thermal expansion (ZTE) magnetic system has a great practical significance having TC higher than 300 K. The parent compound Nd2Fe17, as a magnetocaloric material, has high relative cooling power (RCP) (625 J kg−1 at μ0H = 0–9 T), elevated operational temperature (326 K) and comparatively high entropy change (|ΔSM|max) at TC. Because of these properties Nd2Fe17 can operate as a promising refrigerating system. The critical behaviour of all the four samples is studied by means of the isotherm magnetization in the vicinity of TC. The critical exponents are evaluated using various methods, for instance, modified Arrott plot, critical isotherm, Kouvel–Fisher plot in addition to the study of magnetocaloric effect. From the critical analysis it is revealed that all the four samples belong to different types of universal magnetic class.