Scientists have decoded how heat flows in magnetic semiconductors and resolved a decade-old puzzle in condensed matter physics, a development that has implications for spintronics, magnetic memory and quantum devices. The work identifies mechanisms that alter thermal transport in materials where magnetic and lattice degrees of freedom interact strongly. The discovery opens up new avenues for advanced thermal management in high-performance electronic and magnetic systems.

A team led by Professor Bivas Saha at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, an autonomous institution of the Department of Science and Technology, used temperature-dependent inelastic X-ray scattering to measure phonon lifetimes in high-quality epitaxial chromium nitride (CrN) thin films across the magnetic phase transition. These measurements allowed researchers to track how lattice vibrations interact with magnetic excitations as the material evolves from an ordered magnetic state to a disordered one. The experimental approach provided direct observation of temperature-dependent changes in acoustic phonon behaviour.

The experiments showed that acoustic phonons, the primary carriers of heat, experience strong damping near the Néel temperature owing to intense interactions with magnetic spin fluctuations, while optical phonons follow conventional temperature-dependent behaviour. As long-range magnetic order weakens with rising temperature the team found that acoustic phonon lifetimes increase anomalously, producing enhanced thermal conductivity at raised temperatures contrary to conventional expectations. Advanced atomistic spin-dynamics simulations and first-principles calculations corroborated the observations and established a clear microscopic mechanism linking magnetic fluctuations to anomalous heat conduction.

The findings suggest new strategies for thermal management in spintronic, magnetic memory and quantum devices where heat dissipation is a critical challenge, and they indicate that tuning thermal transport through magnetic degrees of freedom offers a fundamentally new materials design approach. The work was carried out in collaboration with the Indian Institute of Science Education and Research Thiruvananthapuram, Linköping University, and international synchrotron facilities including SPring-eight and DESY, and the study has been published in Science Advances. The results underscore India's growing leadership in materials research.