New study explains unusual heat flow in magnetic semiconductors
Scientists have uncovered how heat flows in magnetic semiconductors, a discovery that could improve the design of next-generation technologies such as spintronic devices, magnetic memory systems and quantum electronics.
The breakthrough research resolves a long-standing puzzle in condensed matter physics and could enable new approaches to thermal management in high-performance electronic systems.
In conventional semiconductors, thermal conductivity typically decreases as temperature rises because lattice vibrations—called phonons, the main carriers of heat—scatter more strongly at higher temperatures. However, certain magnetic semiconductors display an unusual behaviour where thermal conductivity increases once the material crosses its magnetic transition temperature.
One such material is chromium nitride (CrN), widely used in coatings and electronic applications. For years, scientists had struggled to explain the microscopic mechanism behind its unusual heat transport behaviour.
A research team led by Prof. Bivas Saha at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, has now provided direct experimental evidence explaining this phenomenon. The scientists found that strong interactions between phonons and magnetic spin fluctuations play a central role in controlling how heat moves through the material.
Using advanced temperature-dependent inelastic X-ray scattering techniques, the researchers measured phonon lifetimes in high-quality chromium nitride thin films across the magnetic phase transition. The experiments allowed them to observe how lattice vibrations interact with magnetic excitations as the material shifts from an ordered magnetic state to a disordered one.
The results showed that acoustic phonons—the primary carriers of heat—experience strong damping near the Néel temperature, where magnetic ordering changes. As the temperature increases further and magnetic order weakens, phonon lifetimes increase unexpectedly, leading to higher thermal conductivity. In contrast, optical phonons were found to follow the conventional temperature-dependent behaviour.
The findings were further supported by advanced spin-dynamics simulations and first-principles calculations, which together confirmed the link between magnetic fluctuations and heat conduction in the material.
According to Prof. Saha, understanding the interaction between magnetic spins and lattice vibrations opens up new possibilities for managing heat in advanced devices.
Efficient heat dissipation is crucial for technologies such as spintronic processors, magnetic memory systems and emerging quantum devices, where overheating can limit performance and reliability. The ability to control thermal transport through magnetic properties may allow researchers to design materials with adjustable heat flow, enabling faster and more energy-efficient electronics.
The study was carried out through collaboration between JNCASR, IISER Thiruvananthapuram, Linköping University in Sweden, and international synchrotron facilities including SPring-8 in Japan and DESY in Germany.
The findings were recently published in the journal Science Advances, highlighting India’s growing contribution to advanced materials research.
