Magnetic and magnetocaloric properties of Fe2Ta thin films

A magnetocaloric effect (MCE) on rare-earth free Fe2Ta thin films is reported. The structural characterizations carried out using x-ray diffraction and transmission electron microscopy have indicated the formation of a Laves phase in the Fe2Ta film in a MgZn2 type crystal structure. Applying the Maxwell relation to the magnetization (M) vs temperature (T) curves at various fields (H), partial derivative M/partial derivative T vs H curves were integrated to indirectly obtain quantitative information about the isothermal entropy change. A positive MCE with an entropy change as high as 6.9 J/K m(3) at 10 K and a negative MCE with an entropy change as high as -2.0 J/K m(3) at 300 K were observed for the magnetic fields in the range of 0.05-0.5 T. The temperatures at which a crossover in the sign of the entropy change takes place were found to be a function of the field applied that ranged from 121 K at 5000 Oe to 159 K at 1000 Oe. The coexistence of the positive and negative MCE is attributed to a paramagnetic-antiferromagnetic transition in the Fe2Ta system.