Magnetic properties and low-temperature large magnetocaloric effect in the antiferromagnetic HoCu0.33Ge2 and ErCu0.25Ge2 compounds

Magnetic properties and magnetocaloric effect (MCE) of HoCu0.33Ge2 and ErCu0.25Ge2 compounds have been investigated. The compounds were determined to be antiferromagnetic with the Néel temperatures TN = 9 K and 3.9 K, respectively. The critical transition magnetic fields for the metamagnetic transition from antiferromagnetic to ferromagnetic state below TN were determined to be 10 kOe for HoCu0.33Ge2 at 5 K and 6 kOe for ErCu0.25Ge2 at 2 K. Large MCE with the maximal values of magnetic entropy changes (ΔSM) as −10.2 J/kg K at 10.5 K were found in HoCu0.33Ge2 for field changes of 0-70 kOe and −10.5 J/kg K at 5.5 K in ErCu0.25Ge2 for field changes of 0-50 kOe, respectively. The large ΔSM around TN as well as no hysteresis loss made RCuxGe2 competitive candidates as low temperature magnetic refrigerant.