Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Altermagnetic band splitting in 10 nm epitaxial CrSb thin films

Sandra Santhosh, Paul Corbae, Wilson J. Yanez-Parreno, Supriya Ghosh, Christopher J. Jensen, Alexei V. Fedorov, Makoto Hashimoto, Donghui Lu, Julie A. Borchers, Alexander J. Grutter, Timothy R. Charlton, Saurav Islam, Anthony Richardella, K. Andre Mkhoyan, Christopher J. Palmstrøm, Yongxi Ou, Nitin Samarth

TL;DR

This work investigates whether altermagnetic band splitting observed in CrSb persists in thin-film form. Using MBE growth of CrSb(0001) on $SrTiO_3$ with a thin Sb$_2$Te$_3$ buffer, along with comprehensive structural/magnetic characterization and ARPES, the authors map the electronic structure. They find bulk-like three-dimensional altermagnetic spin splitting up to $0.7~\mathrm{eV}$ that survives down to $10~\mathrm{nm}$ thickness at room temperature, with no net CrSb magnetization, indicating robustness of the altermagnetic mechanism to reduced dimensionality. These results establish a lower thickness bound for preserving altermagnetic behavior in CrSb and point to CrSb-based devices as promising platforms for spintronic applications without reliance on strong spin–orbit coupling.

Abstract

Altermagnets are a newly identified family of collinear antiferromagnets with momentum-dependent spin-split band structure of non-relativistic origin, derived from spin-group symmetry-protected crystal structures. Among candidate altermagnets, CrSb is attractive for potential applications because of a large spin-splitting near the Fermi level and a high Neel transition temperature of around 700 K. We use molecular beam epitaxy to synthesize CrSb (0001) thin films with thicknesses ranging from 10 nm to 100 nm. Structural characterization, using reflection high energy electron diffraction, scanning transmission electron microscopy, and X-ray diffraction, demonstrates the growth of epitaxial films with good crystallinity. Polarized neutron reflectometry shows the absence of any net magnetization, consistent with antiferromagnetic order. In vacuo angle resolved photoemission spectroscopy (ARPES) measurements probe the band structure in a previously unexplored regime of film thickness, down to 10 nm. These ARPES measurements show a three-dimensional momentum-dependent band splitting of up to 0.7 eV with g-wave symmetry, consistent with that seen in prior studies of bulk single crystals. The distinct altermagnetic band structure required for potential spin-transport applications survives down to the 10 nm thin film limit at room temperature.

Altermagnetic band splitting in 10 nm epitaxial CrSb thin films

TL;DR

This work investigates whether altermagnetic band splitting observed in CrSb persists in thin-film form. Using MBE growth of CrSb(0001) on with a thin SbTe buffer, along with comprehensive structural/magnetic characterization and ARPES, the authors map the electronic structure. They find bulk-like three-dimensional altermagnetic spin splitting up to that survives down to thickness at room temperature, with no net CrSb magnetization, indicating robustness of the altermagnetic mechanism to reduced dimensionality. These results establish a lower thickness bound for preserving altermagnetic behavior in CrSb and point to CrSb-based devices as promising platforms for spintronic applications without reliance on strong spin–orbit coupling.

Abstract

Altermagnets are a newly identified family of collinear antiferromagnets with momentum-dependent spin-split band structure of non-relativistic origin, derived from spin-group symmetry-protected crystal structures. Among candidate altermagnets, CrSb is attractive for potential applications because of a large spin-splitting near the Fermi level and a high Neel transition temperature of around 700 K. We use molecular beam epitaxy to synthesize CrSb (0001) thin films with thicknesses ranging from 10 nm to 100 nm. Structural characterization, using reflection high energy electron diffraction, scanning transmission electron microscopy, and X-ray diffraction, demonstrates the growth of epitaxial films with good crystallinity. Polarized neutron reflectometry shows the absence of any net magnetization, consistent with antiferromagnetic order. In vacuo angle resolved photoemission spectroscopy (ARPES) measurements probe the band structure in a previously unexplored regime of film thickness, down to 10 nm. These ARPES measurements show a three-dimensional momentum-dependent band splitting of up to 0.7 eV with g-wave symmetry, consistent with that seen in prior studies of bulk single crystals. The distinct altermagnetic band structure required for potential spin-transport applications survives down to the 10 nm thin film limit at room temperature.
Paper Structure (5 sections, 3 figures)

This paper contains 5 sections, 3 figures.

Table of Contents

  1. Introduction
  2. Results and discussion
  3. Epitaxial growth and characterization of CrSb (0001) thin films
  4. Band structure of CrSb thin films
  5. Conclusions

Figures (3)

  • Figure 1: : Characterization of an MBE-grown CrSb thin film on SrTiO$_3$ with a thin Sb$_2$Te$_3$ buffer layer. (a) Schematics of the CrSb unit cell with antiparallel spin sublattices. (b) RHEED patterns of the Sb$_2$Te$_3$ buffer layer and the CrSb film. (c) XRD $2\theta-\omega$ scan of the 31 nm CrSb film with the the rocking curve. (d) XRD phi scan of the SrTiO$_3$ substrate and the CrSb film. (e) HAADF-STEM cross-section image of the Sb$_2$Te$_3$(2 nm)/CrSb(31 nm) heterostructure. Atomic resolution image from the CrSb layer in the purple box (right panel), showing the atomic arrangement of Cr (blue) and Sb (gold). (f) PNR measurements of CrSb(100 nm)/Sb$_2$Te$_3$(2 nm)/SrTiO$_3$ at $T = 300$ K.
  • Figure 2: Photon energy dependent ARPES measurements of 10 nm CrSb thin films.(a) Schematics of the crystal symmetry and (b) the Brillouin zone of CrSb. (c)$\bar{\Gamma} - \bar{M}$ cut at $h\nu = 20$ eV and corresponding $2D$ curvature plot showing evident band splitting. (d)$\bar{\Gamma} - \bar{M}$ cut at $h\nu = 80$ eV and corresponding MDC showing evident band splitting superimposed on a relatively large background. Blue and red lines are guide to the eye. (e)$\bar{\Gamma} - \bar{M}$ cuts from $h\nu = 80$ eV to $100$ eV. Band splitting disappears closer to $h\nu = 100$ eV which corresponds to the bulk $A$ point. (f)$2D$ curvature plots of the spectra shown in (e) to emphasize splitting. The vertical arrow shows a maximum splitting of 700 meV in the $h\nu = 80$ eV data.
  • Figure 3: : He lamp ARPES measurements of CrSb thin films. ARPES spectra of CrSb films (10 nm thickness) along different in-plane momenta direction (a), (b), (c) (top) and corresponding $2D$ curvature images (bottom). The color lines are guides to the eyes for the split bands in CrSb. Fermi surface map (d) of CrSb (10 nm thickness), (e) comparison of the split bands in CrSb films of 10 nm and 100 nm thickness.