Thermodynamic Properties of Heusler Fe2−xCoxMnSi

We investigated the thermodynamic properties of Heusler compounds Fe2−xCoxmnSi (0.00≤x≤2.00). The specific heats CP(T) for compounds with x≤0.1 exhibit a λ-type anomaly arising from spin rearrangements at TR. With increasing x, TR decreases linearly and vanishes at x∼0.169. The magnetic entropy, STR, derived from the magnetic specific heat, Cm(T), released at TR decreases by increasing x. This means the canting angle of spins from the [111] direction decreases by the substitution of Fe atoms with Co atoms, based on the magnetic structure model of Fe2MnSi proposed by Miles et al. For compounds with 0.5≤x, CP(T) in the low-T range can be reproduced by Debye T3 law. The electronic specific heat coefficient decreases monotonically with x.