LAUSR

Abstract Crystal structure and magnetic and thermomagnetic properties of the (TmxPr1-x)2Fe16.5Cr0.5 system have been studied. The alloys with x = 0–0.4 and x = 0.75–1 crystallize into a rhombohedral structure of the Th2Zn17-type and into a hexagonal structure of the Th2Ni17-type, respectively. Both these structures coexist in the concentration range x = 0.5–0.6. The lattice parameters, spontaneous magnetization, and the peak entropy change -ΔSM of the (TmxPr1-x)2Fe16.5Cr0.5 system decrease with increasing Tm content. The Curie temperature of these intermetallic compounds increases non-monotonically from 331 K to 356 K upon partial substitution of Pr for Tm and demonstrates two local minima at x = 0.4 and 0.8. Maximal microdeformations in the alloy with x = 0.8 have been detected by means of X-ray diffraction. The unusual large difference of 25–28 K between the Curie temperatures of the rhombohedral and hexagonal phases in the two-phases compounds with x = 0.5–0.6 has been obtained. The existence of two Curie temperatures causes the temperature interval with maximal values of magnetocaloric effect to be much larger for the two-phases compositions as compared with the single-phase compounds.