Magnetocaloric effect in FeCr soft magnetic nanocrystalline alloys

In this work the magnetocaloric effect in a Fe63.5Cr10Si13.5B9CuNb3 soft magnetic nanocrystalline alloy is analysed. High resolution transmission electron microscocopy indicates the precipitation of the desired nanocrystalline structure (grains around 10nm in size surrounded by a residual amorphous phase) upon suitable treatments of the initial amorphous sample. The temperature dependence of the magnetic entropy variation, Delta S-M(T), calculated from the magnetization curves displays a maximum negative value around the Curie temperature of the residual amorphous phase (T-C,T-a approximate to 180 K). The dependence of Delta S-M(T) on the applied field and its evolution with the nanocrystalline volume fraction indicates the main contribution of the residual amorphous phase to the magnetic entropy change. Some specific low temperature magnetization features (spin freezing) are also analysed in terms of Delta S-M(T). (c) 2007 Elsevier B.V. All rights reserved.