Scientists Decode Heat Transport Mystery in Magnetic Semiconductors

Researchers have solved a long-standing puzzle in condensed matter physics by uncovering how heat moves through magnetic semiconductors—materials crucial for next-generation technologies such as spintronics, magnetic memory, and quantum computing. The study, led by Prof. Bivas Saha at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, has revealed that interactions between magnetic spin fluctuations and lattice vibrations significantly influence heat transport in these materials. The findings have been published in the prestigious journal Science Advances.

In conventional semiconductors, thermal conductivity typically decreases as temperature rises due to increased scattering of phonons—the lattice vibrations responsible for carrying heat. However, certain magnetic semiconductors behave differently. One such material, chromium nitride (CrN), surprisingly shows an increase in thermal conductivity above its magnetic transition temperature, a phenomenon that had remained unexplained for over a decade.

Using advanced temperature-dependent inelastic X-ray scattering techniques, the research team measured phonon lifetimes in high-quality CrN thin films. Their experiments revealed that acoustic phonons—key carriers of heat—experience strong damping near the Néel temperature because of intense interactions with magnetic spin fluctuations.

Interestingly, as temperature rises further and magnetic order weakens, these phonons regain longer lifetimes. This leads to improved heat transport, explaining the unusual increase in thermal conductivity observed in magnetic semiconductors. Optical phonons, however, continued to behave in line with standard thermal expectations.

The team also used atomistic spin-dynamics simulations and first-principles calculations to confirm the experimental observations, establishing a clear microscopic link between magnetic fluctuations and heat conduction.

According to Prof. Saha, the research provides the first direct experimental evidence connecting spin fluctuations with enhanced thermal conductivity in magnetic semiconductors. Understanding these interactions could enable scientists to design materials where heat flow can be controlled using magnetic properties.

This advancement has important implications for high-power spintronic devices, magnetic memory technologies, and emerging quantum systems, where efficient heat dissipation is critical for performance and reliability.

The research involved collaboration between JNCASR, IISER Thiruvananthapuram, Linköping University (Sweden) and international synchrotron facilities including SPring-8 (Japan) and DESY (Germany), highlighting India’s growing role in advanced materials research.

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