Evidence of change in the density of states during the martensitic phase transformation of Ni-Mn-In metamagnetic shape memory alloys

Specific heat measurements were performed at low temperatures for Ni50Mn50−xInx alloys to determine their Debye temperatures (θ_D) and electronic specific heat coefficients (γ). For x ≤ 15, where the ground state is the martensite (M) phase, θ_D decreases linearly and γ increases slightly with increasing In content. For x ≥ 16.2, where the ground state is the ferromagnetic parent (P) phase, γ increases with decreasing In content. Extrapolations of the composition dependences of θ_D and γ in both the phases suggest that these values change discontinuously during the martensitic phase transformation. The value of θ_D in the M phase is larger than that in the P phase. The behavior is in accordance with the fact that the volume of the M phase is more compressive than that of the P phase. On the other hand, γ is slightly larger in the P phase, in good agreement with the reported density of states around the Fermi energy obtained by the first-principle calculations.