Magnetic Domain Walls and Macroscopic Magnetization-Related Elastic and Anelastic Effects during Premartensitic Transition in Ni2MnGa

The temperature and field dependences of internal friction and Young´s modulus are studied using a high-resolution ultrasonic (90 kHz) technique in stoichiometric ferromagnetic Ni2MnGa shape memory alloy close to the premartensitic transformation temperature, TPM, in the demagnetized state and under moderate fields. Several new effects observed like an apparent Young´s modulus softening close to TPM under moderate fields, instead of the hardening outside this range, as well as existing controversies in the apparent elastic and anelastic properties of Ni2MnGa close to TPM are explained by microeddy and macroeddy current relaxations that to date have been disregarded.