Structure, magnetic properties and giant magnetocaloric effect of Tb4Gd1Si2.035Ge1.935Mn0.03 alloy

• 5-2-2 type main phase (monoclinic), 5-4 and 5-3 type secondary phases were obtained.
• A field induced magnetic transition was exhibited at 143 K.
• |ΔSMmax| of the alloy is 22.4 J/kg K when applying field from 0 to 5 T.
• The refrigeration capacity of the alloy is 261 J/kg in a field change of 5 T.
• The average hysteresis loss of the alloy is 30 J/kg for a field change of 5 T.

Tb4Gd1Si2.035Ge1.935Mn0.03 alloy was prepared by arc melting followed by annealing at 1193 K for 168 h. Structural characterizations reveal that monoclinic (Tb, Gd)5Si2Ge2-type phase, secondary phase with orthorhombic 5-4 type structure and hexagonal 5-3 type structure coexist in the alloy. The paramagnetic Curie temperature (θp) is 120 K, indicating that the dominant exchange interaction is ferromagnetic or ferrimagnetic. That the thermal hysteresis of 13 K between heating and cooling and the negative slopes of Arrott plots derived from M–H curves between 116 K and 170 K confirm a typical first-order magnetic transition from ferromagnetism to paramagnetism occurs. The maximum magnetic entropy changes of the Tb4Gd1Si2.05Ge1.95Mn0.03 alloy for magnetic field changes of 0–1 T, 0–2 T, 0–3 T, 0–4 T and 0–5 T are about 3.3, 8.6, 14.0, 18.9 and 22.4 J/kg K, respectively. And the effective refrigeration capacity (RCeff) value is 231 J/kg with a subtracted magnetic hysteresis loss of 30 J/kg for a magnetic field change from 0 to 5 T. Large −ΔSM and RCeff suggest that Tb4Gd1Si2.035Ge1.935Mn0.03 alloy is an attractive potential magnetocaloric material working in the vicinity of 143 K.