Stress Induced and Magnetic Field Enhanced Twin Variants Reorientation in NiMnGa Sinale Crvstal

摘要

The behavior of twin variants reorientation in Ni_(50)Mn_(27.5)Ga_(22.5) single crystal under the applied mechanical stress and magnetic field was investigated. Through three times of compression, the twinning stress was reduced from 4.4MPa to 0.4MPa, and 2.5% stress induced strain was obtained. During the succedent MFIS measurement, with the increase of measurement number of times, the critical field ( μ _0H)_c at which the MFIS jumps became lower, and the corresponding jumping magnetostrain ε_j, and the maximal magnetostrain ε_(max) ascended. At last, a quasi single-variant state was realized, and the sample showed repeatable 6.21% MFIS, which is close to the theoretical value (1-c/a)*100%. The results are discussed from the point of martensitic microstructure evolution.