Improvement of Large Anomalous Hall Effect in Polycrystalline Antiferromagnetic Mn3+xSn Thin Films

In order to improve the large anomalous Hall effect (AHE) in Mn
₃
Sn thin films, we eliminated the co-existing Mn
₂
Sn phase in the films by changing the composition; 50 nm thick polycrystalline Mn
_3±x
Sn thin films were fabricated on SiISiO
₂
substrates by the sputtering method followed by a thermal annealing process in vacuum. The film compositions were Mn
₇₀
Sn
₃₀
(sample-A), Mn
₇₅
Sn
₂₅
(sample-B), and Mn
₈₀
Sn
₂₀
(sample-C) in as-deposited state and were slightly changed to be Mn
₇₅
Sn
₂₅
(sample-A), Mn
₇₇
Sn
₂₃
(sample-B), and Mn
₇₈
Sn
₂₂
(sample-C), respectively, after the annealing at 500 °C. From a structural analysis by X-ray diffractometry, the sample-C was considered to crystallize to Mn
₃
Sn phase without passing the crystallization of Mn
₂
Sn phase at 300 °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 Mn
₂
Sn. 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, σ
_AH
, at the room temperature increased in magnitude, as the content of Mn increased. The sign of σ
_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 Mn
₂
Sn phase in the Mn
₃
Sn thin films with enlarging the Mn content from the stoichiometry. Consequently, we successfully improved the large AHE in polycrystalline antiferromagnetic Mn
₃
Sn thin films.