Thermodynamic Properties of Heusler Fe2-x C ox M n S i

We investigated the thermodynamic properties of Heusler compounds Fe_2-x C o_x m n S i (0.00 ≤ x ≤ 2.00). The specific heats C_P(T) for compounds with x ≤ 0.1 exhibit a λ-type anomaly arising from spin rearrangements at T_R. With increasing x, T_R decreases linearly and vanishes at x ∼ 0.169 . The magnetic entropy, S_TR, derived from the magnetic specific heat, C_m(T), released at T_R 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 , C_P(T) in the low-T range can be reproduced by Debye T³ law. The electronic specific heat coefficient decreases monotonically with x.