New Insights into the Intermartensitic Transformation and Over 11% Magnetic Field‐Induced Strain in 14 m Ni−Mn−Ga Martensite

Stress-induced intermartensitic phase transformation from 10 M to 14 M modulatedmartensite structure is characterized in Ni50.5Mn28.9Ga20.6 at%single crystals, with particular focus on periodic atomic shuffling by in situsynchrotron radiation diffraction. Under compression, along the [001] direction,at 6 MPa, the self-accommodated 10 M single crystal is found to transform to anearly single-variant state. Further stress increase up to 20 MPa triggers intermartensitictransformation to an intermediate, mixed martensite state.Intermartensitic transformation is hereby invoked at a considerably lower stressthan previously reported for NiMnGa alloys. However, the stress level appliedalong the [001] direction does not promote the complete 10 M!14 M martensitetransformation. The 14 M structure is then fully achievable, when a consecutivecompression along the [100] direction is applied. Such mechanically promoted14 M single crystals are stable at room temperature and yield about 11.4%magnetic-field induced strain—being the highest noted up to date for theNiMnGa system