MnxSn100-x thin films with different compositions (x=84, 80, 76, and 74) were fabricated on MgO (111) substrates by radiofrequency magnetron sputtering at room temperature and their properties were evaluated. The samples crystallized into Mn3Sn after thermal annealing at 400°C or higher in vacuum. The Mn80Sn20 film showed only peaks of the (0001) family in out-of-plane XRD profiles, while the other films additionally showed other diffraction peaks indicating their polycrystalline structure. Cross-sectional transmission electron microscopy confirmed successful fabrication of highly c-plane orientated single-phased Mn3Sn thin film in the x=80 sample. The sample possessed a weak ferromagnetic component in the film plane, whose magnitude was comparable with that of bulk Mn3Sn. On the other hand, the out-of-plane magnetization curve had a linear response within ±5T. This magnetic anisotropy is the same as in bulk Mn3Sn. The Hall curve measured with electric current (magnetic field) along the [011¯0] ([0001]) axis indicated a negligibly small negative anomalous Hall effect (AHE). This response was also the same as in bulk Mn3Sn. We thus concluded that the anisotropies of the magnetic properties and AHE of Mn3Sn in a thin-film form are the same as those of bulk.

Highly a-plane-oriented Mn3Sn thin films were grown on m-plane sapphire substrates with low-temperature grown Mn3+xSn buffer layers by sputtering deposition technique, and their crystallinity and magnetic properties were investigated by X-ray diffraction and SQUID magnetometer, respectively. The crystallographic orientations of Mn3Sn domains are found to be sensitively influenced by substrate temperature, thickness and composition ratio of Mn3+αSn buffer layer. The highly a-plane-oriented Mn3Sn film shows slightly different magnetization behavior from randomly oriented Mn3Sn film, while the saturation magnetization Ms and coercivity of the highly a-plane-oriented Mn3Sn film are corresponding to that of single crystal bulk.

In order to improve the large anomalous Hall effect (AHE) in Mn3Sn thin films, we eliminated the co-existing Mn2Sn phase in the films by changing the composition; 50 nm thick polycrystalline Mn3+xSn thin films were fabricated on Si/SiO2 substrates by the sputtering method followed by a thermal annealing process in vacuum. The film compositions were Mn70Sn30(sample-A), Mn75Sn25(sample-B), and Mn80Sn20(sample-C) in as-deposited state and were slightly changed to be Mn75Sn25(sample-A), Mn77Sn23(sample-B), and Mn78Sn22(sample-C), respectively, after the annealing at 500 degrees C. From a structural analysis by X-ray diffractometry, the sample-C was considered to crystallize to Mn3Sn phase without passing the crystallization of Mn2Sn phase at 300 degrees C, differently from the sample-A. The saturation magnetization, MS, of the sample-A significantly increased below 250 K, corresponding with the Curie temperature of Mn2Sn. On the other hand, MS did not show significant changes with cooling temperature in the samples-B and -C. An AHE was observed at the room temperature in all the samples. The anomalous Hall conductivity, sigma(AH), at the room temperature increased in magnitude, as the content of Mn increased. The sign of sigma(AH) changed from negative to positive in the sample-A with cooling temperature. On the other hand, the sign remained negative in the sample-C. These differences might be due to the elimination of co-existing Mn2Sn phase in the Mn3Sn thin films with enlarging the Mn content from the stoichiometry. Consequently, we successfully improved the large AHE in polycrystalline antiferromagnetic 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.