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Crystal structure, magnetic and transport characteristics of Ni2-x Mn1+x
Sn Heusler series have been studied with the emphasis on chemical
disorder effects. It is shown that the structure and the disorder
character in these series can be predicted by using simple rules. Ni-2
MnSn is a ferromagnetic, congruent melting phase, which crystallizes
cubic in the L2(1) structure type. By increasing x, Ni and Mn atoms
randomly mix and occupy the heterocubic sites of the regular Heusler
structure, and the magnetic structure becomes ferrimagnetic. The total
magnetic moment m(sat) decreases linearly in the range 0.2 <= x <= 1,
while the Curie temperature T-C increases. At low Mn content (x < 0.2),
the unit cell volume shows anomalous behavior, characterized by constant
m(sat) and T-C. Electrical resistivity, Seebeck coefficient, and thermal
conductivity strongly depend on the amount of disorder, which increases
with the Mn content. Results of first-principle calculations based on
the coherent potential approximation (CPA) alloy theory for the magnetic
and electrical properties are in reasonable agreement with the simple
rules and all experimental data. (C) 2014 Elsevier Ltd. All rights
reserved.
