[Paper Review] Epitaxial stabilization of magnetic GdAuSb/LaAuSb superlattices

Patrick J. Strohbeen, Soohyun Im+8 more|arXiv (Cornell University)|Mar 6, 2026

Iron-based superconductors research0 citations

TL;DR

The paper demonstrates epitaxial growth of GdAuSb films and GdAuSb/LaAuSb superlattices on Al2O3, revealing similar near-Fermi electronic structures to LaAuSb with a Gd-induced 9 eV f-state and two magnetic transitions in superlattices due to interlayer exchange.

ABSTRACT

We report the epitaxial stabilization of GdAuSb films and GdAuSb/LaAuSb superlattices via molecular beam epitaxy on (0001)-oriented Al$_{2}$O$_{3}$ substrates. GdAuSb crystallize in the Au-Au dimerized YPtAs structure type (space group $P6_{3}/mmc$), the same structure as the Dirac semimetal LaAuSb. Angle-resolved photoemission spectroscopy (ARPES) measurements show similar near $E_F$ bandstructures for GdAuSb and LaAuSb, plus a rigid band shift for GdAuSb towards more hole-like behavior and core-like Gd $4f$ states $\sim 9$~eV below the Fermi energy. LaAuSb/GdAuSb superlattices exhibit sharp superlattice fringes by X-ray diffraction and atomically-precise interfaces by scanning transmission electron microscopy. Superlattices display two transitions in temperature-dependent resistvity, compared to a single Néel temperature for thick GdAuSb films. Superlattices of $Ln$AuSb materials ($Ln=$ rare earth) with atomically abrupt interfaces offer a new epitaxial platform for control of magnetic and topological order via tunable intralayer exchange and reduced dimensionality.

Motivation & Objective

• Demonstrate epitaxial stabilization of GdAuSb in the YPtAs-type structure on Al2O3(0001).
• Synthesize atomically sharp GdAuSb/LaAuSb superlattices with well-defined interfaces.
• Characterize electronic structure and magnetic properties to explore magnetism-topology interplay in 19-valence LnAuSb materials.

Proposed method

• Molecular beam epitaxy growth of GdAuSb and LaAuSb on Al2O3(0001) at 650 °C.
• X-ray diffraction to confirm phase, c-axis doubling, and mosaicity.
• Angle-resolved photoemission spectroscopy to compare near-EF bandstructure and identify Gd 4f states.
• Density functional theory calculations (WIEN2k, GGA+SO) for band structure comparison.
• Scanning transmission electron microscopy to verify atomically sharp interfaces in superlattices.
• Resistivity, SQUID magnetometry, and magnetotransport to study magnetic transitions.

Figure 1: (a) Survey $\omega$ -2 $\theta$ x-ray diffraction scan comparing the new GdAuSb compound to the previously reported LaAuSb alloy. 000 l reflections are labeled, substrate reflections are labeled with asterisks (*). (b) Zoom-in on (0002) reflection for GdAuSb and LaAuSb films to highlight t

Experimental results

Research questions

• RQ1 Can GdAuSb be epitaxially stabilized in the YPtAs structure on Al2O3 substrates?
• RQ2 Do GdAuSb/LaAuSb superlattices exhibit atomically abrupt interfaces and tunable interlayer magnetic coupling?
• RQ3 How does Gd incorporation affect near-Eg Fermi surface and presence of Gd 4f states compared to LaAuSb?
• RQ4 What magnetic transitions arise in GdAuSb/LaAuSb superlattices and how are they related to interlayer exchange?

Key findings

• GdAuSb grows epitaxially in the Au–Au dimerized YPtAs structure with c-axis doubling, confirmed by 000l reflections and Kiessig fringes indicating an 85.5 nm film thickness.
• GdAuSb exhibits a similar near-EF bandstructure to LaAuSb with a rigid band shift and a distinct Gd 4f peak near 9 eV, consistent with core-like f-states.
• GdAuSb/LaAuSb superlattices show sharp, atomically precise interfaces as evidenced by XRD superlattice fringes and high-quality cross-sectional STEM imaging.
• Superlattices display two resistivity-related magnetic transitions, with T_N1 ≈ 17.85 K and a second transition at T_N2 ≈ 6.13 K, indicating interlayer exchange effects.
• Interfacial design enables tuning of magnetic coupling between GdAuSb layers via LaAuSb spacers, illustrating control of magnetism in 19-valence LnAuSb systems.

Figure 2: Electronic structure of thick GdAuSb and LaAuSb films. (a) Angle-integrated photoemission spectroscopy of the valence bands for GdAuSb and LaAuSb. The Gd 4f states are on a split scale at 0.1x the original scale to fit the states into the same plot. (b) Angle-resolved photoemission spectro