Strong magnetocaloric effect induced by spin reorientation transitions in epitaxial Ho thin films

Magnetocaloric effect (MCE) in an antiferromagnetic holmium (Ho) film is studied near the spin reorientation temperatures. A series of magnetization isotherms from 60 to 150 K around the Neel temperature, T-N approximate to 130 K were recorded for both in-plane and out-of-plane magnetic field orientations. A change in entropy, Delta S-M of -5 J/kgK was found near T-N for an in-plane field orientation. A large change in Delta S-M of -11.8 J/kg K due to a fan-helix spin transition at T = 90 K is observed for an in-plane field orientation. Spin transition at both T-N and at the fan-helix transition exhibit larger MCE in the in-plane field orientations in comparison with the perpendicular orientation. The value of the refrigerant capacity extracted from the temperature dependence of Delta S-M (T) is found to be larger for the "in- plane" orientation by a factor of two.