Influence of chemical pressure in Sn-substituted Ni2MnGa Heusler alloy: Experimental and theoretical studies

The influence of the chemical pressure on the magneto-structural properties of the Ni2MnGa Heusler alloy after a gradual substitution of Ga by Sn atoms was theoretical and experimentally studied in this work. Our data clearly show that an expansion of the L2(1)-cell volume due Sn-substitution causes a diminution of the internal structural stress and favors the austenitic state in low temperatures where martensitic phase should prevail. It is also shown that the total magnetization reduces with increasing Sn-content, a behavior explained by a reduction of the Ni-magnetic moment, since an increase of Mn-magnetic moment was theoretically calculated. The Sn-substitution effect in the Ni2MnGa compound is similar to that found in experiments performed under high applied magnetic fields, which means that in both cases there is an increase of the L2(1) cell-volume favoring the austenitic state in low temperatures. Magnetization values in martensitic state of the pure Ga-compound systematically reduce after consecutive M(T) thermal cycle recorded at 5 mT; an effect not yet reported within our knowledge and attributed here to modifications in local magnetic anisotropies during the field cycles. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4757951]