Ferromagnetic resonance in nanotwinned Ni–Mn–Ga film undergoing martensitic transformation
J.Kharlan1, V.A. L’vov1,2, and V.O. Golub1
1Institute of Magnetism of the National Academy of Sciences and Ministry of Education and Science of Ukraine 36-b Vernadsky blvd., Kyiv 03142, Ukraine
2Taras Shevchenko National University of Kyiv, 4 G Academician Glushkov Ave., Kyiv 01601, Ukraine
Received December 23, 2019, published online April 24, 2020
The ferromagnetic resonance (FMR) in the shape memory alloys (SMAs) exhibiting structural cubic-tetragonal phase transition has been studied. The influence of instability and spatial inhomogeneity of crystal lattice on the FMR spectra of twinned ferromagnetic SMAs films has been analyzed using statistical model of ferromagnetic mar-tensite. It has been shown that the abnormally strong temperature dependence of lattice parameters of martensitic film gives a noticeable contribution to the temperature dependence of the resonance value of external magnetic field. The narrowing of the resonance peak, which had been experimentally observed on cooling of the film slightly below the Curie temperature, has been explained. It is argued that the martensitic films are good candidates for the experimental study of local elastic strains influence on the shape of the FMR peak.
Key words: ferromagnetic resonance, martensitic transformation, thin film, crystal lattice instability.