Nanoscale Tracking of the High-Temperature Spin-State Transition in LaCoO ₃

The high-temperature spin and electronic transitions in LaCoO₃ have recently been leveraged to create neuromorphic (brain-inspired) devices. While these devices have shown the potential for impactful functionality in next-generation computing systems, the nanoscale dynamics of the spin and electronic transitions that underlie their operation are not well understood. Inhomogeneities related to interfaces, electrode contacts, strain, and crystal defects can all affect device performance, making nanoscale characterization of the transitions essential for producing consistent and reliable devices. Here, we demonstrate the first nanoscale in situ measurement of the spin transition in LaCoO₃ at device-relevant temperatures (25-325 °C) over length scales of tens of nanometers using STEM-EELS. This measurement is enabled by an Al₂O₃ coating, which prevents unwanted reduction of the LaCoO₃ specimen at high temperature and vacuum. The detailed understanding of LaCoO₃ transition dynamics enabled by such measurements will be crucial for optimizing LaCoO₃-based neuromorphic devices and increasing reliability for real-world application.