Magnetic and Magnetocaloric Properties in the Non-stoichiometric Fe2+xTa1-x (x = 0–0.25) Alloys

In this work, the crystal structure, microstructure, magnetic transition (MT), and magnetocaloric effect (MCE) in the non-stoichiometric Fe2+xTa1-x (x = 0–0.25) alloys were investigated. All the Fe2+xTa1-x (x = 0–0.25) alloys are confirmed to crystallize in the MgZn2 type Laves phase crystal structure where the 4(f) site was occupied by Ta atoms and partially doped by Fe atoms and the other Fe atoms occupied the 2(a) and 6(h) sites. Enhanced magnetic and magnetocaloric properties have been achieved by with the increases of Fe content. The Curie temperature (TC) increases gradually with increasing Fe content x which are 36, 118, 172, and 173 K for x = 0, 0.10, 0.18, and 0.25, respectively. Reversible MCE in the Fe2+xTa1-x alloys has been observed which is related to a second-order MT from paramagnetic to ferromagnetic state, the values of peak magnetic entropy change (– ΔSMmax) as well as the refrigerant capacity (RC) and relative cooling power (RCP) are all increasing gradually with increasing Fe content x. The values of – ΔSMmax are 0.26, 0.48, 0.69, and 0.76 J/kgK with the magnetic field change of 0–7 T for x = 0, 0.10, 0.18, and 0.25, and the corresponding value of RC (RCP) are 20.8 (25.9), 48.5 (62.5), 64.0 (82.8), and 68.4 (89.5) J/kg, respectively.