Ab initio modeling of martensitic transformations (MT) in magnetic shape memory alloys

Abstract The magnetic field-induced (MFI) changes of the electronic, magnetic and phonon properties of magnetic shape memory Heusler alloys Ni–Mn–Ga and Ni–Mn–In are discussed on the basis of first-principles calculations. Without an external magnetic field, the lattice instability to shear wave propagation in [1 1 0] direction shows up in the calculation as softening of the TA 2 ζ [1 1 0] ( 2 π / a ) mode at ζ ≈ 1 3 . The ab initio modeling of magnetic field effects shows that the phase (austenite or martensite) is favored which has larger magnetization. This is in agreement with experiments on Ni–Mn–In, for which the martensitic transformation (MT) can be shifted by 40 K to lower temperatures in an external field of 5 T.