We have investigated the magnetic ground state properties of the quantum spin trimer compound strontium hydroxy copper chloride SrCu(OH)3Cl using bulk magnetization, specific heat measurements, nuclear magnetic resonance (NMR), and electron spin resonance (ESR) spectroscopy. SrCu(OH)3Cl consists of layers with isolated Cu2+ triangles and hence provides an opportunity to understand the magnetic ground state of an isolated system of \textit{S} = 1/2 arranged on an equilateral triangle. Although magnetization measurements do not exhibit a phase transition to a long-range ordered state down to \textit{T} = 2 K, they reveal the characteristic behavior of isolated trimers with an exchange of J=154~K. The Curie-Weiss behavior changes around 50--80~K, as is also seen in the NMR spin-lattice relaxation rate. In zero magnetic field, our specific heat data establish a second-order phase transition to an antiferromagnetic ground state below \textit{T}= 1.2 K. We have drawn a magnetic field-temperature (H-T) phase diagram based on the specific heat measurements. The ESR data show divergence of the linewidth at lower temperatures, which precedes the phase transition to an antiferromagnetic long-range ordered state with unconventional critical exponents. The temperature variation of the g-factor further confirms the antiferromagnetic phase transition and reflects the underlying magneto-crystalline anisotropy of the compound.
@article{arxiv.2401.12098,
title = {SrCu(OH)$_3$Cl, an ideal isolated equilateral triangle spin $S$ = 1/2 model system},
author = {Sudip Pal and Petr Doležal and Scott A. Strøm and Sylvain Bertaina and Andrej Pustogow and Reinhard K. Kremer and Martin Dressel and Pascal Puphal},
journal= {arXiv preprint arXiv:2401.12098},
year = {2024}
}