Quantum spin-liquid in Ba₃CuSb₂O₉ epitaxial thin films

Hexagonal perovskite materials are emerging quantum spin liquid (QSL) systems providing a fertile ground to realize novel quantum phenomena. The epitaxially grown thin films of such materials offer a compelling approach to utilize exotic quantum phases for device applications with better control over the structure. We fabricate the intriguing QSL triple perovskite Ba₃CuSb₂O₉epitaxially onto a MgO (100) substrate by pulsed laser deposition technique as well as in bulk form for comparison. The presence of only (00l) parallel planes of Ba₃CuSb₂O₉in x-ray diffraction validates the epitaxial growth of the thin film. Temperature-dependent magnetization of thin film reveals no magnetic ordering down to 400 mK, with a large antiferromagnetic Curie-Weiss temperature (θCW≈-11.68 K). This indicates strong magnetic frustration and QSL behaviour, similar to bulk Ba₃CuSb₂O₉. The presence of magnetic correlations at low temperature (in the quantum spin liquid state) is further confirmed by analysing the low temperature magnetic isotherms. These experimental findings underscore the potential of this quantum material for its use in quantum technologies.