Magnetic field-induced twin boundary motion in polycrystalline Ni–Mn–Ga fibres

Abstract

Magnetic field-induced twin boundary motion leading to large magnetic field-induced strain of ∼1.0% was established in polycrystalline Ni50.9Mn27.1Ga22.0 (at.%) fibres at room temperature (∼60–100 μm in diameter and ∼3 mm in length). The fibres' grains are as large as the fibre diameter and of random orientation. At room temperature, a ferromagnetic 5M martensite is found. Magnetic field-induced twin boundary motion was indicated by magnetic measurements and validated by electron backscatter diffraction (EBSD). The application of a magnetic field shifts the equilibrium temperature of martensite and austenite by ∼0.4 K T−1, which agrees with calculations using the Clapeyron–Clausius approach.