Giant anisotropy of magnetocaloric effect in TbMnO3single crystals

Abstract

The magnetocaloric effect (MCE) in TbMnO${}_{3}$ single crystals was investigated by isothermal magnetization curves for the $\mathit{ab}$ plane at low temperatures. Large magnetic entropy change, $\ensuremath{\Delta}{S}_{M}$ $=$ \ensuremath{-}18.0 J/kg K, and the refrigerant capacity, RC $=$ 390.7 J/kg, are achieved near the ordering temperature of Tb${}^{3+}$ moment (${T}_{N}^{\mathrm{Tb}}$) under 70 kOe along the $a$ axis. Furthermore, the TbMnO${}_{3}$ single crystal exhibits a giant MCE anisotropy. The difference of $\ensuremath{\Delta}{S}_{M}$and RC between the $a$ and $b$ axes is field and temperature dependent, which reaches maximum values of 11.4 J/kg K and 304.1 J/kg, respectively. By taking magnetocrystalline anisotropy into account, the rotating $\ensuremath{\Delta}{S}_{M}$within the $\mathit{ab}$ plane can be well simulated, indicating that the anisotropy of $\ensuremath{\Delta}{S}_{M}$is directly contributed from the magnetocrystalline anisotropy. Our finding for giant MCE anisotropy in TbMnO${}_{3}$ single crystals explores the possibility of using this material for magnetic refrigerators by rotating its magnetization vector rather than moving it in and out of the magnet.