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초록

Competing exchange interactions in frustrated three-dimensional spin lattices offer a promising route to realize rich physical phenomena, including spin liquids with exotic low-energy excitations. In this work, we focus on the three-dimensional frustrated magnet MgCrGaO4, where Cr3+ ions occupy a pyrochlore-like network. Due to intrinsic disorder and partial occupation of the pyrochlore sites by magnetic ions, the actual structure highlights the famous closed loops of the pyrochlore lattice. Our thermodynamic, electron spin resonance (ESR), muon spin relaxation (& micro;SR), and inelastic neutron scattering (INS) techniques detect no signature of magnetic order or spin freezing down to 57 mK, despite a sizable exchange interaction (J = 58 K) between Cr3+ moments. Below the characteristic exchange energy scale, all probes reveal the emergence of antiferromagnetic short-range spin correlations, corroborated by magnetic diffuse scattering in the wave vector dependence of low-energy magnetic excitations centered on Q = 1.5 & Aring;-1 in inelastic neutron scattering experiments. The low-temperature specific heat follows a near-quadratic dependence suggesting the presence of nontrivial low-energy excitations. These results establish MgCrGaO4 as a rare three-dimensional spin liquid with exotic excitations, offering a strong impetus for the experimental realization of spin liquids in higher-dimensional frustrated quantum magnets.

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