Microstructure and magnetic property changes in martensitic Ni52Mn29Ga19 thin films by 3 MeV proton irradiation

The martensitic Ni-Mn-Ga thin film irradiated by 3 MeV proton with different proton fluence from 5.0 × 10¹⁵ p/cm² to 5.0 × 10¹⁶ p/cm² was investigated with regard to the microstructure and magnetic properties. The transmission electron microscopy (TEM) results show that seven-layered modulated (7M) martensitic Ni₅₂Mn₂₉Ga₁₉ films reorientation occures at the proton fluence values of 5.0 × 10¹⁵ p/cm². The non-modulated (NM) martensites were produced with a proton fluence of 2.0 ×10¹⁶ p/cm², and their reorientation occurs at the proton fluence values of 5.0 × 10¹⁶ p/cm². By varying the proton fluences the magnetism has been able to tune. In particular, the Curie temperature and magnetization of irradiated Ni₅₂Mn₂₉Ga₁₉ films is lower than the unirradiated film.