Direct observation of magnetic domains by Kerr microscopy in a Ni-Mn-Ga magnetic shape-memory alloy

摘要

The magnetic domains in a magnetic shape-memory Ni-Mn-Ga alloy were observed by magneto-optical Kerr microscopy using monochromatic blue LED light. The domains were observed for both single- and multivariant ferroelastic states of modulated martensite. The multivariant state with very fine twins was spontaneously formed after transformation from high-temperature austenite. For both cases, bar domains separated by 180° domain walls were found and their dynamics was studied. A quasidomain model was applied to explain the domains in the multivariant state.