Study on the Structure, Magnetic Properties, and Transport Properties of Hexagonal MnNiGa Thin Films

Keywords: Hexagonal structure, MnNiGa, magnetron sputtering, perpendicular magnetic anisotropy, spintronics. Hexagonal MM'X materials represent a class of promising novel functional materials with magnetic phase-transition properties and have attracted considerable attention in recent years. In this study, we systematically investigated the crystal structure, magnetic properties, and transport characteristics of ternary MnNiGa thin films prepared by direct-current magnetron sputtering and using first-principles calculations under different sputtering temperatures. X-ray diffraction analysis confirmed that the MnNiGa thin films exhibit a hexagonal structure of the Ni2In type (space group P63/mmc). Scanning electron microscopy images revealed the influence of sputtering temperature on the surface morphology of the thin films.

　　Keywords: Hexagonal structure, MnNiGa, magnetron sputtering, perpendicular magnetic anisotropy, spintronics

　　The hexagonal MM'X materials represent a class of novel functional materials with potential magnetic phase-transition properties, and have attracted considerable attention in recent years. In this study, we systematically investigated the crystal structure, magnetic properties, and transport characteristics of ternary MnNiGa thin films deposited by DC magnetron sputtering, using first-principles calculations. X-ray diffraction analysis revealed that the MnNiGa thin films exhibit a hexagonal structure of the Ni2In type (space group P63/mmc). Scanning electron microscopy images demonstrated the influence of sputtering temperature on the surface morphology of the films, whereas energy-dispersive spectroscopy indicated that the composition of the films remained virtually unchanged across different sputtering temperatures. The magnetic measurements showed that all the films exhibited ferromagnetic behavior and possessed magnetic anisotropy. We also measured both magnetoresistance (MR) and Hall resistance. The results indicated that the MR was negative and exhibited a linear relationship with the applied magnetic field. In the Hall effect, the anomalous Hall effect (AHE) played a dominant role, and the AHE was primarily driven by skew scattering mechanisms. Band-structure calculations revealed that the bulk MnNiGa material has a spin polarization rate of 33%; however, along the G-A direction, the spin polarization rate reached as high as 100%. These findings suggest that the hexagonal MnNiGa material holds promise as a candidate for spintronic applications.

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