Structural, magnetic and magnetocaloric properties of Heusler alloys Ni50Mn38Sb12 with boron addition

We report on the structural, magnetic and magnetocaloric properties of the Ni50Mn38Sb12Bx alloys in term of boron addition with x=1, 3 and 5. We have found that both the paramagnetic-ferromagnetic austenitic transition (T-C) and the ferromagnetic-antiferromagnetic martensitic transition (T-M) are sensitively influenced by the boron addition: T-C tends to increase, while T-M decreases with increasing boron concentration. Temperature dependent X-ray diffraction in the range of 200-500 K clearly shows an evolution of the structural transformation from orthorhombic to cubic structure phase transition on heating for the x=1 and 3 samples. Strikingly, the addition of boron atoms into the lattice favours the ferromagnetic ordering relatively to the antiferromagnetic arrangement below T-M. This consequently affects on the magneto-structural transition as well as on the size of magnetocaloric effect. (C) 2011 Elsevier B.V. All rights reserved.