Multistage development of short-range spin correlations and weak magnetic order in the two coupled trillium lattices of K2Fe2(MoO4)(PO4)2
Dr. Raman Sankar and his group, in collaboration with Prof. Kwang-Yong Choi at Sungkyunkwan University (Republic of Korea) investigated the Trillium lattices, where magnetic ions form a chiral network of corner-sharing triangles, offer a three dimensional magnetic framework that can host fragile classical spin-liquid states. Herein, we report on the magnetization, specific heat, electron spin resonance (ESR), and muon spin relaxation (µSR) of K2Fe2(MoO4)(PO4)2 single crystals. Magnetization measurements reveal strong antiferromagnetic interactions coexisting with weak magnetic order at TN = 5.2K, as evidenced by a λ-like anomaly observed in the magnetic susceptibility, a critical enhancement of the muon spin relaxation rate and the wipeout of the ESR signal as the temperature approaches TN. Above TN, two distinct developments of short-range spin correlations are identified at TH = 34K and TL = 10K,supported by magnetic specific heat anomalies and the temperature dependence of the ESR linewidth and g factor. Upon cooling below TN, an anomaly appears at T∗ = 3.2K in thermodynamic observables and the muon spin relaxation rate, indicative of spin reorientation driven by residual interactions. Despite the presence of magnetic order, µSR experiments reveal dynamically fluctuating spins persisting even in the ordered state. Moreover, the suppression of TN under applied magnetic fields (μ0H ⩾ 2T) suggests that K2Fe2(MoO4)(PO4)2 constitutes a promising candidate for exploring field-induced spin-liquid behavior in three-dimensionally coupled trillium lattices.
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Journal Links: https://journals.aps.org/prb/pdf/10.1103/s6y4-2n8m