MgZn<inf>2</inf>-type {Ho, Er, Tm}FeGa rare earth compounds: Crystal structure and magnetic properties

The crystal structure of new hexagonal MgZn2-type {Ho, Tm}FeGa compounds (space group P63/mmc, N 194, hP12) has been established using powder X-ray diffraction studies. The magnetic properties of polycrystalline MgZn2-type ErFeGa compound have been studied using bulk magnetization data. ErFeGa exhibits ferromagnetic ordering at TC = 77 K and field sensitive antiferromagnetic-like ordering at Tm ~ 58 K in field of 100 Oe and Tm ~ 10 K in field of 5 kOe. The paramagnetic susceptibility follows Curie-Weiss law with effective paramagnetic moment per formula unit (Meff/fu) of 9.59 μB and paramagnetic Weiss temperature (ΘP) of 27 K. At 2 K, ErFeGa exhibits hard magnetic properties with remanent magnetization per formula unit (Mres/fu) of 3.7 μB, coercive field (Hcoer) of 8.2 kOe and critical field (Hcrit) of ~9.6 kOe. The magnetocaloric effect of ErFeGa has been calculated in terms of isothermal magnetic entropy change (ΔSm) and maximum ΔSm values are −5.5 J/kg K for a field change of 0–50 kOe (relative cooling power RCP50 kOe ~ 410 J/kg), −13.0 J/kg K for a field change of 0–140 kOe (RCP140 kOe ~ 1230 J/kg) at 70 K and +1.7 J/kg K for a field change of 0–10 kOe at 10 K (RCP10 kOe ~ 34 J/kg).