Anomalous Hall effect in polycrystalline Mn3Sn thin films

A polycrystalline Mn3Sn thin film was fabricated on a Si/SiO2 substrate by radio frequency magnetron sputtering with co-deposition from Mn and Sn targets followed by a thermal annealing process in vacuum. From a structural analysis by transmission electron microscopy, the Mn2Sn phase was found to co-exist in the film. The thin film exhibited weak ferromagnetic behavior, and the saturation magnetization, MS, of the ferromagnetic component of the Mn3Sn phase was about 10 emu/cc at room temperature, which is six times larger than the reported value for bulk Mn3Sn single crystals. MS significantly increased below 250 K, corresponding to the Curie temperature of Mn2Sn. An anomalous Hall effect (AHE) was observed in the film in the examined temperature range of 50 K to 350 K. The anomalous Hall conductivity, σAH, was negative at room temperature like the bulk Mn3Sn, and the estimated value of –18.5 Ω−1·cm−1 was comparable to that of the bulk Mn3Sn. The sign of AHE was changed to positive below 240 K, which might be caused by the co-existing Mn2Sn phase. We thus concluded that a large AHE in antiferromagnetic materials was observed in a thin film form of Mn3Sn.