Abstract
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.
Highlights
An anomalous Hall effect (AHE)1,2 with a significant amplitude, as strong as that of ferromagnetic materials, was observed in a bulk form of Mn3Sn in 2015.3 Mn3Sn is an antiferromagnetic material with a kagome lattice in its c-plane
We discovered that a Mn-rich composition was necessary to eliminate other phases which degraded the AHE magnitude in the samples
MgO substrates were heated at 650○C for 30 minutes by a lamp heater in a vacuum chamber in order to remove the adsorbed moisture from the surface. 50-nm-thick MnxSn100-x thin films were deposited by radiofrequency magnetron sputtering with co-deposition from the Mn and Sn targets at room temperature
Summary
An anomalous Hall effect (AHE) with a significant amplitude, as strong as that of ferromagnetic materials, was observed in a bulk form of Mn3Sn in 2015.3 Mn3Sn is an antiferromagnetic material with a kagome lattice in its c-plane. The 120○-ordered Mn spins cancel each other in the kagome triangle, and a negligibly small spontaneous magnetic moment is induced with small canting from the triangle spin structure in the c-plane.. The AHE in Mn3Sn is exceedingly large compared with this small spontaneous magnetic moment. Since the AHE has been empirically confirmed to be related to the magnetic moment, this unconventional phenomenon has attracted significant attention. Recent studies have revealed that the mechanism is crossing points near the Fermi energy in its band dispersion diagram.
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