Anomalous and topological Hall effects in epitaxial thin films of the noncollinear antiferromagnet Mn3Sn

Abstract

Noncollinear antiferromagnets with a D019 (space group = 194, P63/mmc) hexagonal structure have garnered much attention for their potential applications in topological spintronics. Here, we report the deposition of continuous epitaxial thin films of such a material, Mn3Sn, and characterize their crystal structure using a combination of x-ray diffraction and transmission electron microscopy. Growth of Mn3Sn films with both (0001) c-axis orientation and (404 ̅ 3) texture is achieved. In the latter case, the thin films exhibit a small uncompensated Mn moment in the basal plane, quantified via magnetometry and x-ray magnetic circular dichroism experiments. This cannot account for the large anomalous Hall effect simultaneously observed in these films, even at room temperature, with magnitude σxy (µ0H = 0 T) = 21 Ω -1 cm -1 and coercive field µ0Hc = 1.3 T. We attribute the origin of this anomalous Hall effect to momentumspace Berry curvature arising from the symmetry-breaking inverse triangular spin structure of Mn3Sn. Upon cooling through the transition to a glassy ferromagnetic state at around 50 K, a peak in the Hall resistivity close to the coercive field indicates the onset of a topological Hall effect contribution, due to the emergence of a scalar spin chirality generating a real-space Berry phase. We demonstrate that the polarity of this topological Hall effect, and hence the chiral-nature of the noncoplanar magnetic structure driving it, can be controlled using different field cooling conditions.

Omnidirectional Control of Large Electrical Output in a Topological Antiferromagnet

“…[ 17,34,37 ] Moreover, the room‐temperature TR‐odd responses remain useful in the same concentration range while the non‐stoichiometry of Mn 3 Sn shifts the Fermi energy by changing the number of conduction electrons. [ 17,21,29,38 ] While the ITS structure is coplanar, recent studies have found that the topological Hall effect may also arise from the non‐coplanar spin structure stabilized in the magnetic domain wall [ 39,40 ] or in the low‐temperature cluster glass phase. [ 17,40 ]…”

“…[ 17,21,29,38 ] While the ITS structure is coplanar, recent studies have found that the topological Hall effect may also arise from the non‐coplanar spin structure stabilized in the magnetic domain wall [ 39,40 ] or in the low‐temperature cluster glass phase. [ 17,40 ]…”

Magnetic and Electronic Properties of Weyl Semimetal Co2MnGa Thin Films

“…They are characterized by a lack of inversion symmetry or broken time-reversal symmetry, resulting in two-fold degenerate band-touching points (Weyl nodes) with opposite chirality formed in momentum space [ 3 , 5 , 10 , 11 , 12 ]. The Weyl nodes act as quantized sources and sinks of Berry curvature, which in turn lead to intriguing transport properties, such as the anomalous Hall effect [ 13 , 14 , 15 , 16 , 17 , 18 ], the anomalous Nernst effect [ 19 , 20 , 21 , 22 ], magneto-optical responses [ 23 ] and the chiral anomaly [ 24 , 25 ]. Recently, some ferromagnetic compounds were proposed to be time reversal symmetry breaking Weyl semimetals (WSMs).…”

Large Hall Signal due to Electrical Switching of an Antiferromagnetic Weyl Semimetal State

“…Recent developments in the thin film fabrication processes have led to the realization of various spintronic devices using the Mn 3 Sn film. [ 26–34 ] In the antiferromagnetic memory made of the Mn 3 Sn/heavy metal multilayers, the electrical current may switch the direction of the ferroic order of the magnetic octupole (Figure 1b). Thus, the information is stored as the polarity of AHE, which may be read out through the sign and magnitude of the anomalous Hall voltage.…”