Effect of water treatment on microstructure and magnon thermal transport in spin ladder compound Sr12Y2Cu24O41

The spin ladder compounds (Sr,Ca,La,Y)14Cu24O41, known for their large magnon thermal conductivity, show great promise for thermal management and spin caloritronic applications. However, these materials are unstable in humid air and can decompose when exposed to moisture. The effect of decomposition on magnon thermal transport in these materials remains unreported. Understanding this effect is crucial for developing spin ladder compounds for practical applications. This study highlights the distinct impact of water treatment on the microstructure and thermal transport properties in single crystals and polycrystals of the spin ladder compound Sr12Y2Cu24O41. Our findings indicate that water treatment substantially decreases the magnon thermal conductivity of polycrystals, while the magnon thermal conductivity of single crystals remains largely unaffected. This significant difference can be attributed to the presence of grain boundaries in polycrystals, which allow water to penetrate the bulk of the polycrystalline samples. The reaction with water results in the formation of CuO and SrCO3 nanostructures, which scatter both phonons and magnons, thereby reducing both lattice and magnon thermal conductivity. To mitigate the adverse effects of water interaction, we developed a simple sputter coating method for spin ladder samples. Notably, the metal-coated samples demonstrated sustained high thermal conductivity, even after extended exposure to water treatment. Our study provides useful insights into the practical applications of the cuprate-based quantum magnets in thermal management and energy conversion.