Er2Fe14B single crystal as magnetic refrigerant at the spin reorientation transition

In this paper we study the specific heat under magnetic field c(p)(H(a), T) and the magnetic field induced isothermal entropy change Delta s(H(a), T) of Er(2)Fe(14)B by direct calorimetry and magnetic measurements. We find that the spin reorientation temperature is T(SR) = 322.8 +/- 0.1 K and the entropy change is Delta s = 0.735 +/- 0.005 J kg(-1) K(-1). The measured data are interpreted by a model of the magnetization process taking into account a temperature-dependent uniaxial anisotropy constant K(1)(T), the magnetic field energy, and the effect of the demagnetizing field. The model is able to describe the essential features of the measured Delta s(H(a), T) in terms of reversible rotation of the magnetization induced by the magnetic field. From the model we find that the entropy change has a magnetic field independent saturation value.Delta s(K)(T) = 735 - 5.5 x 10(-3) (T - T(SR)) and that the magnetic field amplitude increases the temperature range over which the effect is observed as Delta T = beta mu(0)H with beta = 54 K T(-1). (C) 2011 American Institute of Physics.