Reaching the equilibrium state of the frustrated triangular Ising magnet Ca3Co2O6

• Published in: Physical review. B 2022-01, Vol.105 (2)
• Main Authors: Nekrashevich, Ivan, Ding, Xiaxin, Balakirev, Fedor, Yi, Hee Taek, Cheong, Sang-Wook, Civale, Leonardo, Kamiya, Yoshitomo, Zapf, Vivien S.
• Format: Article
• Language: English
• Subjects: antiferromagnetism; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; exchange interaction; feromagnetism; ferrimagnetism; frustrated magnetism; magnetic phase transitions; magnetic susceptibility; magnetic texture; magnetization dynamics; magnetostriction; Monte Carlo methods; order parameters; phase diagrams
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.105.024426

Ca3Co2O6 is a frustrated magnet consisting of a triangular arrangement of chains of Ising spins. It shows regular magnetization steps versus magnetic field every 1.2 T that are metastable with very slow dynamics. This has puzzled the community for many years and given rise to numerous potential theories. Here we approach the problem by seeking the elusive magnetic equilibrium state at T=2 K. To this end, we explore two approaches: (1) bypassing the slow dynamics produced by changing fields by instead field-cooling directly to the target temperature and (2) quantum annealing in transverse magnetic fields. While we observe no measurable effect of the quantum annealing in fields up to 7 T, which is likely due to the large Ising anisotropy of Co spins in this material, we find that for the field cooling in longitudinal fields we achieve the predicted equilibrium 1/3 magnetization. We perform Monte Carlo simulations of the ground state phase diagram and we also simulate the quantum annealing process and find good agreement between experiment and theory. Thus we present an investigation of the elusive ground state properties of the canonical frustrated triangular system Ca3Co2O6.