ScholarWorks@성균관대학교

초록

The subtle interplay between competing degrees of freedom, crystal electric fields, and spin correlations can lead to exotic quantum states in 4 f ion-based frustrated triangular lattice antiferromagnets. We present the crystal structure, thermodynamic and muon spin relaxation (mu SR) studies of the 4 f ion-based frustrated magnet Ba4YbReWO12, wherein Yb3+ ions constitute a triangular lattice. The magnetic susceptibility does not show any signature of spin freezing down to 1.9 K or long-range magnetic ordering down to 0.4 K. The low-temperature Curie-Weiss fit to the inverse magnetic susceptibility data reveals a weak antiferromagnetic exchange interaction, which is corroborated by the fit of magnetic specific heat data following the J1 - J2 model with the nearest-neighbor-exchange interaction of J1 approximate to -0.197 K between the Jeff = 1/2 states of the Yb3+ moments in the lowest Kramers doublet. The lowest Kramers ground state doublet is well separated from the first excited state with a gap of Delta CEF = 278 K, as evidenced by our mu SR experiments that support the realization of Jeff = 1/2 at low temperatures. The specific heat experiments do not detect a phase transition down to 56 mK. The magnetic specific heat shows a broad maximum at 90 mK suggesting a disordered ground state with short-range spin correlations. The associated magnetic entropy release at low temperatures is consistent with that expected for the Jeff = 1/2 state. The zero-field mu SR measurements show neither the signature of spin freezing nor a phase transition, at least down to 43 mK. Our results suggest a dynamic, disordered ground state in this Jeff = 1/2 frustrated triangular lattice antiferromagnet. Ba4RReWO12 (R=rare earth) offers a viable platform to realize intriguing quantum states borne out of spin-orbit coupling and frustration.

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