Strong magnetocaloric effect induced by spin reorientation transitions in epitaxial Ho thin films
In this work, 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 Néel temperature, $T_N$ ≈ 130 K were recorded for both in-plane and out-of-plane magnetic field orientations. A change in entropy, Δ$S_M$ of –5 J/kgK was found near $T_N$ for an in-plane field orientation. A large change in Δ$S_M$ of –11.8 J/kg K due to a fan-helix spin transition at $\textit{T}$ = 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 Δ$S_M(T)$ is found to be larger for the “in- plane” orientation by a factor of two.