microstructures

Recently, large magnetic contribution to thermal conductivity has been observed in some cuprates with strong antiferromagnetic coupling. One prominent example is the spin ladder compound Sr₁₄Cu₂₄O₄₁ with an incommensurate layered structure. Steady-state thermal transport measurements of single crystals revealed a large anisotropic ratio of thermal conductivity due to the magnons propagating along spin ladders. Previous studies have been devoted to understand the coupling of magnons with phonons and electrons in Sr₁₄Cu₂₄O₄₁ single crystals; however, the effects of boundaries and defects on anisotropic magnon transport have been under-examined. Here, we investigate the thermal transport in Sr₁₄Cu₂₄O₄₁ microrods, which are prepared by co-precipitation synthesis. TEM studies indicate that these microrods are single crystals grown preferentially along the spin ladder axis. The thermal conductivity of Sr₁₄Cu₂₄O₄₁ microrods prepared at different temperatures is measured using a four-probe thermal transport measurement method. The thermal conductivity contribution and mean free paths of magnons are evaluated using a kinetic model of 1D magnon transport. Our results show pronounced effects of defects and boundaries on anisotropic magnon thermal transport in the magnetic microstructures.