Imaging thermal properties at the microscale is crucial for unveiling the structure-property relation and developing next-generation thermal management materials. Here, we apply a frequency-domain thermoreflectance (FDTR) microscopy for imaging the thermal conductivity and interfacial thermal conductance of thermal interface materials (TIMs). A fixture customized for imaging thermal properties of TIMs is developed, where the sample is sandwiched between a silica slide coated with a metal transducer and a substrate wafer, and the thermal transport properties are extracted using a bidirectional thermal model. The thermal conductivity of TIMs loaded with thermally conductive particles is profiled with micrometer resolution, and significant local non-uniformity is observed. Pressure-dependent FDTR imaging during loading and unloading reveals the local redistribution of conductive filler particles. Correlative micro-computed tomography reveals that the high thermal conductivity regions correspond to the aggregation of thermally conductive particles. Further statistical analysis of the FDTR image unveiled the asymmetrical and long-tailed probabilistic distribution of thermal conductivity values. Through statistical modeling, we demonstrate that this asymmetry originates from the lognormal size distribution of microparticles. Our work sheds light on the structure-property relation between microstructure and thermal conductivity distribution of TIMs at the microscale.

Thermal Hall effect (THE) refers to the phenomenon whereby, in a magnetic field, when a longitudinal heat current flows through a material, the heat carriers are deflected, thereby generating a transverse temperature difference between the two lateral edges. The transition from electrical to thermal transport enables this effect to involve a wide range of carriers, thereby providing a unique perspective for investigating complex quantum states in condensed matter physics. THE is increasingly becoming a powerful probe of neutral excitations in materials and is used to explore multifield control phenomena in magneto-thermal-electrical coupled systems. Advances in the field of THE have significantly advanced the study of condensed matter systems under extreme conditions (low temperatures and strong magnetic fields) and have laid the groundwork for exploring novel magneto-thermal-electrical effects in quantum materials. This review systematically reviews recent theoretical and experimental progress on THE, with particular attention to the underlying heat carriers. Through an in-depth analysis of the transport mechanisms of different carriers, quantum material systems that can be used to investigate multicarrier coupled transport are identified, which will significantly facilitate the synergistic control of magneto-thermal-electrical transport in complex interacting systems. Finally, we propose a novel in situ, multiparameter integrated characterization method that enables simultaneous and precise measurement of magnetic, thermal, and electrical parameters on the same micro/nanoscale samples. This approach not only overcomes the limitations of bulk materials but also serves as a key experimental platform for revealing the mechanisms of multicarrier coupled transport in micro/nano samples.