High quality epitaxial thin films and exchange bias of antiferromagnetic Dirac semimetal FeSn

Abstract

FeSn is a topological semimetal (TSM) and kagome antiferromagnet (AFM) composed of alternating Fe3Sn kagome planes and honeycomb Sn planes. This unique structure gives rise to exotic features in the band structures such as the coexistence of Dirac cones and flatbands near the Fermi level, fully spin-polarized 2D surface Dirac fermions, and the ability to open a large gap in the Dirac cone by reorienting the Néel vector. In this work, we report the synthesis of high-quality epitaxial (0001) FeSn films by magnetron sputtering. Using FeSn/Py heterostructures, we show a large exchange bias effect that reaches an exchange field of 220 Oe at 5 K, providing unambiguous evidence of antiferromagnetism and strong interlayer exchange coupling in our films. Field cycling studies show steep initial training effects, highlighting the complex magnetic interactions and anisotropy. Importantly, our work provides a simple, alternative means to fabricate FeSn films and heterostructures, making it easier to explore the topological physics of AFM TSMs and develop FeSn-based spintronics.

Magnetotransport Study of Dirac Metal FeSn Thin Films Grown on Silicon Substrates

“…The unit cell parameters, a = b = 5.298 Å and c = 4.448 Å, are taken from the Ref. [9] for the calculation of the XRD peaks (black curve in Figure 3) and the crystal structure in Figure 4.…”

“…The XRD patterns for 30 nm FeSn grown on Si(100), Si(111), and STO(111) can be found in Supporting Information (Figure S2 and S3, Supporting Information,). All the observed XRD peaks of FeSn thin films on different substrates can be indexed based on a hexagonal crystal structure with [9] for the calculation of the XRD peaks (black curve in Figure 3) and the crystal structure in Figure 4.…”

“…[1][2][3][4][5][6] One of the most prominent iron-based compounds, FeSn, has attracted a lot of research interest recently. [6][7][8][9][10][11] FeSn is an intermetallic antiferromagnetic compound that crystallizes in a hexagonal crystal structure, belonging to the space group of P6/mmm (191). [10,11] It consists of alternating 2D layers of Fe 3 Sn (Kagome structured) and Sn 2 (stanine) stacked over each other where the Kagome structured layer has a Fe corner-sharing triangle network whose center of the hexagon is occupied by Sn atoms.…”

“…[8] There are several reports on thin films of FeSn grown on a variety of substrates such as STO, LaAlO 3 (LAO), Al 2 O 3 , and niobium-doped STO. [6,9,11,12,14] Epitaxial single-crystal FeSn thin film grown on STO (111) substrates has shown antiferromagnetic ordering at T N = 353 K and a residual resistivity ratio (RRR) ρ xx (300 K)/ρ xx (2 K) = 24. [14] Although there have been a handful of studies on thin-film FeSn, it has always been a challenge to grow a pure/single phase of FeSn irrespective of the choice of substrate, including on silicon.…”

Recent Progress on 2D Kagome Magnets: Binary TmSnn (T = Fe, Co, Mn)

“…attributed the non‐linearity of Hall resistivity also found in the high quality epitaxial FeSn(0001)/Ru/(111) Pt/(0001)/Al 2 O 3 films prepared by magnetron sputtering to the less ferromagnetic components in the films. [ 59 ] They verified the antiferromagnetism in FeSn/Permalloy (Py, Ni/Fe 81/19 wt%) heterostructures by a significant exchange bias effect, and proposed a strong exchange interaction between Py spin and the uncompensated spin in the interface FeSn(0001) plane. The presence of large exchange bias fields and intense training effects allowed them to determine the existence of multiple equivalent easy axes in FeSn films.…”