Magnetocaloric and electrical transport properties of selenospinels A<inf>0.9</inf>Cu<inf>0.1</inf>Cr<inf>2</inf>Se<inf>4</inf> (A = Cd and Zn)

Magnetization, electrical resistivity and Seebeck coefficient of ACr2Se4 (A = Cd and Zn) spinels with 10% Cu-substitution at A-site have been studied. While Cd0.9Cu0.1Cr2Se4 orders ferromagnetically at 129 K (TC), Zn0.9Cu0.1Cr2Se4 displays complex antiferromagnetic order at TN = 20 K. Magnetocaloric effect (MCE) in the vicinity of the magnetic transition has been estimated in terms of isothermal magnetic entropy change (ΔSm). The maximum values of ΔSm for Cd0.9Cu0.1Cr2Se4 and Zn0.9Cu0.1Cr2Se4 are about −4.2 J/kg K and −3.4 J/kg K respectively at 133 K and 48 K for a field change from 0 to 70 kOe. Electrical resistivity shows Mott variable range hopping behaviour below 50 K. Large positive thermoelectric power values are observed below 300 K in both Cd0.9Cu0.1Cr2Se4 and Zn0.9Cu0.1Cr2Se4.