Influence of deformation on the microsructure and magneic properties of Heusler alloys

Abstract

This paper presents the results of studies of the effects of deformation obtained by the method of multiple isothermal forging on the microstructure and magnetic properties of the NiMnGa alloy system. It is shown that the microstructure of the initial alloy during deformation undergoes changes, grain size decreases and a two-component structure is formed. The magnetic domain structure of the original and deformed alloys was visualized by magnetic force microscopy. It is shown that the distortion of the domain shape is associated with the presence of a martensitic relief and grain boundaries, 180-degree magnetic domains are continuous within the crystallites, while they cross the flat parallel boundaries of the martensite plates. The study of temperature and field magnetization dependences of the initial and isothermal forging samples demonstrates an insignificant magnetization decrease and a shift of the phase transition temperature toward low temperatures. It’s concluded that deformation by the isothermal forging method can be considered as a way to correct the phase transition temperature in NiMnGa alloys with preservation of magnetization.

Keywords

• heusler alloys
• martensitic relief
• multiple isothermal forging
• micro and nanostructure
• magnetic domain structure
• magnetostructural transition