Stabilization of the Collinear Plateau Phase by Thermal Fluctuations in the Diluted Triangular Lattice Antiferromagnet Rb_(1-x)K_xFe(MoO₄)₂
Glazkov V.N., Krastilevskiy I.A.

Received: July 25, 2025

DOI: 10.31857/S0044451025090147

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The triangular lattice antiferromagnet RbFe(MoO₄)₂ orders antiferromagnetically in a planar 120-structure below K. A striking feature of RbFe(MoO₄)₂ magnetic phase diagram is the presence of collinear «1/3-plateau» magnetic phase, which is stabilized by thermal and quantum fluctuations at magnetic fields in the vicinity of 1/3 of a saturation field. Quenched disorder caused by impurities is predicted to act against the effect of fluctuations and to suppress collinear plateau phase [V. S. Maryasin and M. E. Zhitomirsky, Phys. Rev. Lett. 111, 247201 (2013)]. Balance between «dynamic» thermal and quantum fluctuations and «static» impurity-induced disorder is temperature-sensitive, which allows thermal fluctuations to take over the effect of static disorder and leads to the restoration of the fluctuation-stabilized «1/3-plateau» phase on heating. Here we present experimental results directly confirming this prediction and demonstrating re-establishment of the plateau-like phase in the diluted Rb_(1-x)K_xFe(MoO₄)₂ sample at moderate dilution level x=0.15 on increasing the temperature.