Cu3Te2O5(OH)4: A Frustrated Two-Dimensional Quantum “Magnetic Raft” as a Possible Pathway to a Spin Liquid

We report a combined experimental and theoretical study of the hitherto unknown compound Cu3Te2O5(OH)4 that comprises an original network of ferromagnetic (FM; J 1 = −100 K with strong next-nearest neighbor exchanges J NNN = 50 K) chains and alternating antiferromagnetic (AFM; J 2 ∼ 148 K, and J 2′ ∼ 125 K) chains arranged in a so-called S = 1/2 two-dimensional “magnetic raft” spin–lattice. The two one-dimensional spin sublattices are interconnected by weaker exchanges (J d ∼ 40 K), which create tetrahedral Cu4 knots between the cross-linked “raft” legs, bringing about strong magnetic frustration. The magnetic susceptibility and specific heat show the absence of magnetic ordering down to 1.8 K hampered by fully frustrated Cu1 spins. High-field magnetization reveals a one-third magnetization plateau that is stable up to 33 T, which conveys the fingerprint of the individual AFM and FM chains. Magnetic entropy shows a two-stage Schottky-like release, implying the thermal decoupling of magnetic sublattices. Our work establishes that Cu3Te2O5(OH)4 can serve as a prominent platform for discovering sought-after quantum spin liquids in chemistry and physics.