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Magnetic phase diagram of ErB4 as explored by neutron scattering

Simon Flury1,2,*, Wolfgang J. Simeth1,2, Danielle R. Yahne1,2, Manisha Islam1,2, Igor Plokhikh2, Daniel G. Mazzone2, Eric D. Bauer3, Priscila F. S. Rosa3, Romain Sibille2 et al.

Oksana Zaharko2, Dariusz J. Gawryluk2, and Marc Janoschek1,2,†

  • *Contact author: simon.flury@psi.ch
  • †Contact author: marc.janoschek@psi.ch
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Phys. Rev. B 112, 224441 – Published 24 December, 2025

DOI: https://doi.org/10.1103/m3wx-4v6k

Abstract

The tetragonal 4f-electron intermetallic ErB4 is characterized by strong Ising anisotropy along the tetragonal c axis. The magnetic moments on the erbium sites can be mapped onto a Shastry-Sutherland lattice, resulting in geometrical frustration. At zero magnetic field ErB4 exhibits collinear columnar antiferromagnetic (CAFM) order below TN=15.4K. In the presence of a magnetic field parallel to the c axis, ErB4 exhibits a plateau at 1/2 of the saturation magnetization MS, which arises at a spin-flip transition at H1 = 1.9 T. Fractional magnetization plateaus and other exotic spin phases are a well-established characteristic feature of frustrated spin systems. Monte Carlo simulations propose that ErB4 is an ideal candidate to feature a spin supersolid phase in close vicinity of H1 between the CAFM and M/MS=1/2 plateau (HP) phase. Here, we combine single-crystal neutron diffraction and inelastic neutron scattering to study the magnetic phase diagram and the crystal electric-field (CEF) ground state of ErB4. Our measurements as a function of magnetic field find no signature of the spin supersolid phase but allow us to determine the magnetic structure of the HP phase to be of the up-up-up-down (uuud) type consistent with an Ising material. The magnetic moment μCEF = 8.96µB expected from the CEF configuration determined by our inelastic neutron-scattering measurements is also consistent with the ordered moment observed in neutron diffraction, showing that the moments are fully ordered and close to the Er3+ free ion moment (9.6 µB).

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Phys. Rev. B 112, 224441– Published 24 December, 2025
  • Received 10 September 2024
  • Revised 12 November 2025
  • Accepted 2 December 2025
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