Abstract
In this paper we study the specific heat under magnetic field cp(Ha,T) and the magnetic field induced isothermal entropy change Δs(Ha,T) of Er2Fe14B by direct calorimetry and magnetic measurements. We find that the spin reorientation temperature is TSR=322.8±0.1 K and the entropy change is Δs=0.735±0.005Jkg-1K-1. The measured data are interpreted by a model of the magnetization process taking into account a temperature-dependent uniaxial anisotropy constant K1(T), the magnetic field energy, and the effect of the demagnetizing field. The model is able to describe the essential features of the measured Δs(Ha,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: ΔsK(T)=0.735-5.5×10-3(T-TSR) and that the magnetic field amplitude increases the temperature range over which the effect is observed as ΔT=βμ0H with β=54 KT-1.
Published Version
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