Rotating field entropy change in hexagonal TmMnO3 single crystal with anisotropic paramagnetic response

The anisotropy of magnetic field- induced entropy change, -Delta S, was investigated in a hexagonal TmMnO3 single crystal at a temperature range of 2-50 K. The value of -Delta S along the c axis reaches a maximum of 8.73 J/kg K at 17 K in a field of 70 kOe, which is 20 times larger than that along the a axis. Our finding suggests that the rotating field entropy change -Delta S-R(alpha) from the a to c axis is attributed not only to magnetocrystalline anisotropy, but to thermal fluctuations.