Influence of the atomic order on the magnetic characteristics of a Ni-Mn-Ga ferromagnetic shape memory alloy

The influence of the atomic order on the magnetic properties has been analyzed in a polycrystalline Ni49.5Mn28.5Ga22 ferromagnetic shape memory alloy prepared by arc melting under Ar atmosphere. Different thermal treatments have been performed to modify the order degree of the alloy. The effect of the different thermal treatments on the magnetic and structural characteristics has been analyzed by superconducting quantum interference device (SQUID) and differential scanning calorimetry (DSC) measurements. The magnetic and structural properties of the alloys are modified as a consequence of the atomic order change. The martensitic transformation temperatures increase as long as the order degree increases. On the other side, the Curie temperature and magnetization saturation also reflect the order degree of the alloy but seems to be linked to the particular order of the Mn sub-lattice. (c) 2008 Elsevier B.V. All rights reserved.