Optical and magneto-optical studies of martensitic transformation in Ni-Mn-Ga magnetic shape memory alloys
Abstract
Optical and magneto-optical properties of single crystal of Ni50.1Mn28.4Ga21.5 magnetic shape memory alloy during its transformation from martensite to austenite phase were systematically studied. Crystal orientation was approximately along {100} planes of parent cubic austenite.
X-ray reciprocal mapping confirmed modulated 10M martensite phase. Temperature depended measurements of saturation magnetization revealed the martensitic transformation at 335K during heating.
Magneto-optical spectroscopy and spectroscopic ellipsometry were measured in the sample temperature range from 297 to 373K and photon energy range from 1.2 to 6.5 eV. Magneto-optical spectra of polar Kerr rotation as well as the spectra of ellipsometric parameter Psi exhibited significant changes when crossing the transformation temperature.
These changes were assigned to different optical properties of Ni-Mn-Ga in martensite and austenite phases due to modification of electronic structure near the Fermi energy during martensitic transformation.