First principles investigations of the magnetic properties and martensitic transformation in Mn2NiB Heusler alloy

Abstract The presented results of first principles calculations show that the tetragonal deformation of Mn 2 NiB with inverse Heusler structure (Hg 2 CuTi) leads to a decrease in the total energy of the system. Two minima in the dependence of the total energy of the compound on the c/a ratio are found for c/a = 0.94 and c/a = 1.33. The results indicate that the c/a ratio of 1.33 yields the smallest energy at T = 0 K. The total energy difference between the states of Mn 2 NiB at c/a = 1.33 and c/a = 1.0 is estimated to be of about 345 K. The Mn 2 NiB transition from cubic to tetragonal structure can help to avoid a singularity at the Fermi level in the density of states of the parent compound with the cubic Hg 2 TiCu structure. Martensitic (tetragonal) and austenitic (cubic) phase of Mn 2 NiB are found to be ferrimagnetic with antiparallel aligned Mn spin moments. The contributions of 3 d states from Ni(C)-e g , Mn(A)-e g and Mn(B)-t 2g to the minority peak near the Fermi level are discussed. These states in DOS for minority spins is shifted towards higher energy with the tetragonal distortion c/a > 1.0. Upon the martensitic transition, the intensities of peaks corresponding to the DOS change, taking mutually reversed values.