Monte Carlo Simulations of Thermal Hysteresis in Ni‐Mn‐Based Heusler Alloys

Abstract

We present a study of the thermal hysteresis that takes place across the magnetostructural phase transition of the Ni-Mn-based Heusler alloys. The results have been obtained by means of first-principles calculations and Monte Carlo simulations based on the proposed Potts-Blume-Emery-Griffiths Hamiltonian involving magnetic and elastic degrees of freedom. First, separating the structural and magnetic contributions, we calculate the phase diagram including the martensitic transformation as a function of ratio between exchange structural constants in martensite and austenite (K/J). It is shown that the width of the thermal hysteresis depends on K/J and it is found to increase at a ratio of K/J between 0.20 and 0.37. A similar trend is also observed for the Landau free energy expansion. The evolutions of the magnetization and deformation order parameter of alloys studied under various applied magnetic fields are simulated as functions of temperature upon heating and cooling cycles. Furthermore, under high applied fields the nonlinear shift of dT m =dH ext and change of hysteresis width according to the relation between magnetostructural interaction constants (U 1 and U 2 ) are observed. The results obtained with the Monte Carlo routine are discussed and demonstrated a good agreement with experimental data.

Heat capacity, thermal conductivity and magnetocaloric effect in Heusler alloy Ni-=SUB=-47-=/SUB=-Mn-=SUB=-40-=/SUB=-Sn-=SUB=-13-=/SUB=-

“…Phase transitions, magnetic and structural properties in the studied Ni-Mn-Sn system have been studied theoretically and experimentally in sufficient detail [1][2][3][4][5][6][7][8][9][10]. Papers [11][12][13][14][15] are dedicated to a detailed study of the structure, magnetic and magnetocaloric properties of the studied compound Ni 47 Mn 40 Sn 13 .…”