Elasticity and magnetism of Ni 2 MnGa premartensitic tweed

Magnetic, magneto‐elastic and elastic measurements were used to characterize the thermal evolution of the premartensite phase of Ni 2 MnGa. The premartensitic transition is shown to correspond to a sharp maximum of magnetostriction and a pronounced minimum of the (110) 〈 1 1 ‾ 0 〉 shear stiffness (the c ′ elastic coefficient); no additional softening of the c ′ coefficient prior to the martensitic transformation was observed. In contrast, a significant softening of the (100) 〈 010 〉 stiffness (the c 44 elastic coefficient) was observed in the vicinity of the martensitic transition, while this coefficient is fully unaffected by the premartensitic transition. A simple two‐dimensional model of the tweed is presented to explain this mutual independence between the c ′ and c 44 shears and the effect of tweed formation on both of them.