Magnetocaloric response of amorphous and nanocrystalline Cr-containing Vitroperm-type alloys

• Study of magnetocaloric effect of amorphous and nanocrystalline Cr-Vitroperm alloys.
• Cr content decreases the magnetocaloric response and the Curie temperature.
• Nanocrystallization reduces MCE and modifies TC in a non-monotonous way.
• The large difference between TC of phases decreases MCE of composite.

The broad compositional range in which transition metal (TM) based amorphous alloys can be obtained, yields an easily tunable magnetocaloric effect (MCE) in a wide temperature range. In some TM-based alloys, anomalous behaviors are reported, as a non-monotonous trend with magnetic moment (e.g. FeZrB alloys). Moreover, in certain Cr-containing Vitroperm alloys anomalously high values of the magnetic entropy change were published. In this work, a systematic study on MCE response of Cr-containing amorphous alloys of composition Fe74-xCrxCu1Nb3Si15.5B6.5 (with x=2, 8, 10, 12, 13, 14 and 20) has been performed in a broad Curie temperature range from 100 K to 550 K. Curie temperature and magnetic entropy change peak of the amorphous alloys decrease with the increase of Cr content at rates of −25.6 K/at% Cr and −54 mJ kg−1 K−1/at% Cr, respectively, following a linear trend with the magnetic moment in both cases. The presence of nanocrystalline phases has been considered as a possible cause in order to explain the anomalies. The samples were nanocrystallized in different stages, however, the magnetocaloric response decreases as crystallization progresses due to the large separation of the Curie temperatures of the two phases.