The electronic and magnetic properties and topological Hall effect in hexagonal MnNiGa alloy films by varying Mn contents

We report on a systematic study of the electronic, magnetic properties and topological Hall effect (THE) in the hexagonal MnNiGa alloy films as a function of Mn contents. It was found that the MnNiGa alloy films with pure hexagonal structure and flat surface could be obtained on oxidized Si(001) substrates through magnetron sputtering. An analysis of magnetic and transport properties reveals that MnNiGa alloy films show a magnetic structure transformed from ferromagnetic to ferrimagnetic structure with increasing Mn contents, accompanied by a maximum of the saturation magnetization near the stoichiometric composition. We have further investigated the stability of the large THE emerging in MnNiGa alloy films with various Mn contents over a wide temperature-magnetic field region. In contrast to bulk MnNiGa alloy, a reversion of the sign of THE was clearly observed in Mn-rich MnNiGa alloy film, indicating the THE of MnNiGa alloy can be manually controlled by varying Mn contents. - Highlights: • Co-sputtered hexagonal MnNiGa alloy films with various Mn contents have been prepared. • MnNiGa alloy films with various Mn contents exhibit a complex magnetic behavior. • In contrast to bulk MnNiGa alloys, a reversion of the sign of topological Hall effect was observed. • Topological Hall effect of MnNiGa alloy films can be controlled by varying Mn content.