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Magnetic-field-driven phase switching in the antiferromagnetic Mott insulator Ca3(Ru0.99Ti0.01)2O7

Ksenia S. Rabinovich1,*, Tim Priessnitz1,*, Nils Gross1,*, George Jackeli1,2, Maximilian J. Krautloher1, Pascal Reiss1, Eberhard J. Goering1, Jurgen H. Smet1, Bernhard Keimer1 et al.

Alexander V. Boris1,†

  • *These authors contributed equally to this work.
  • †Contact author: A.Boris@fkf.mpg.de
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Phys. Rev. B 114, 185134 – Published 30 September, 2026

DOI: https://doi.org/10.1103/z696-28zn

Abstract

A bandwidth-controlled antiferromagnetic Mott-insulating phase in Ca3(Ru1−xTix)2O7 is realized through isovalent substitution of the Ru site. For a dilute substitution with only 1% Ti, the Mott insulator ground state remains nearly degenerate with the ground state of pristine Ca3Ru2O7, where the Ru moments are ferromagnetically aligned within the metallic RuO2 bilayers, which are stacked in an antiferromagnetic fashion. The exceptionally shallow free-energy landscape of this doped compound arises from intertwined electron–electron and electron–lattice interactions. This makes its magnetic and transport properties highly sensitive to external perturbations. We systematically investigated magnetic-field-induced phase switching in Ca3(Ru0.99Ti0.01)2O7 to explore its magnetic H−T phase diagram. With the field applied along the easy b axis, parallel to the antiferromagnetic moments, the magnetization exhibits a first-order spin-flop transition at ≈6T, indicating reorientation of the Ru moments perpendicular to the field. The transition is accompanied by a decrease in the electrical resistance, but the spin-flop phase remains insulating. Above 10.5T, all Ru moments align with the b axis, resulting in a forced ferromagnetic metallic phase. In contrast, neither spin-flop nor forced ferromagnetic phases are observed up to 14T when the field is applied along the a axis. While the electronic kinetic energy and the electron–lattice coupling contribute to the free-energy balance of this system, the resulting H−T phase diagram is remarkably simple and closely resembles that of a canonical anisotropic antiferromagnet, albeit with substantially renormalized critical fields.

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Phys. Rev. B 114, 185134– Published 30 September, 2026
  • Received 22 June 2026
  • Accepted 10 September 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by Max Planck Society.

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