Study of the magnetic properties and magnetocaloric effect in RCo2B2 (R = Tb, Dy and Ho) compounds

The magnetic properties and magnetocaloric effect (MCE) of RCo2B2 (R = Tb, Dy and Ho) have been investigated by the magnetization and heat capacity measurements. For TbCo2B2, a paramagnetic to antiferromagnetic (PM – AFM) magnetic transition was observed under low fields, whereas a field-induced metamagnetic transition from antiferromagnetic to ferromagnetic (AFM – FM) has been observed with the application of higher magnetic field. An inverse MCE was found, which is attributed to the nature of AFM state under low field and at low temperatures for TbCo2B2, a normal MCE was observed under higher magnetic field change which is related to the first order metamagnetic transition from AFM to FM state. A large reversible MCE was observed for DyCo2B2 and HoCo2B2, which is related to a second order magnetic transition from PM to FM state. For a field change of 5 T, the maximum values of magnetic entropy change (−ΔSMmax) reach 6.2, 12.1 and 12.2 J kg−1 K−1 for R = Tb, Dy and Ho, respectively. The corresponding relative cooling power values are evaluated to be 1.8, 2.9 and 2.3 J/cm3.