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 to 100μm in diameter and ~3mm in length). The fibres' grains were as large as the fibre diameter and of random orientation. At room temperature, a ferromagnetic 5M martensite was found. Magnetic field-induced twin boundary motion was indicated by magnetic measurements and validated by electron back-scatter diffraction. The application of a magnetic field shifts the equilibrium temperature of martensite and austenite by ~0.4K/T, which agreed with calculations performed using the Clapeyron–Clausius approach.

Magnetic Field-Induced Twin Boundary Motion in Polycrystalline Ni–Mn–Ga Fibres. N.Scheerbaum, O.Heczko, J.Liu, D.Hinz, L.Schultz, O.Gutfleisch: New Journal of Physics, 2008, 10[7], 073002 (8pp)