Magnetic properties and magnetocaloric effect in the RCu₂Si₂ and RCu₂Ge₂ (R=Ho, Er) compounds

The magnetic properties and magnetocaloric effect (MCE) in RCu₂Si₂ and RCu₂Ge₂ (R=Ho, Er) compounds have been investigated. All these compounds possess an antiferromagnetic (AFM)-paramagnetic (PM) transition around their respective Neel temperatures. The RCu₂Si₂ compounds undergo spin-glassy behavior above Neel temperature. Furthermore, a field-induced metamagnetic transition from AFM to ferromagnetic (FM) states is observed in these compounds. The calculated magnetic entropy changes show that all RCu₂Si₂ and RCu₂Ge₂ (R=Ho, Er) compounds, especially, ErCu₂Si₂ exhibits large MCEs with no thermal hysteresis and magnetic hysteresis loss. The value of -Δ S_M^max reaches 22.8J/Kg K for magnetic field changes from 0 to 5T. In particular, for field changes of 1 and 2T, the giant reversible magnetic entropy changes -Δ S_M^max are 8.3 and 15.8J/kg K at 2.5K, which is lower than the boiling point of helium. The low-field giant magnetic entropy change, together with ignorable thermal hysteresis and field hysteresis loss of ErCu₂Si₂ compound is expected to have effective applications in low temperature magnetic refrigeration.