At the University of Liège, my colleagues and I have been deeply engaged in exploring the microscopic interactions that drive magnetic behavior in real-world materials—especially when these materials are exposed to heat, disorder, or both.
In two complementary studies, we focused on how phonons (or lattice vibrations) and magnons (or spin excitations) affect transport and magnetic properties in ferromagnetic metals like iron, nickel, and permalloy (Ni₈₁Fe₁₉), a widely used alloy in spintronics.
While answering to theoretical questions of how the fundamental excitation interacts into complex materials, our goal was to help industries that rely on magnetism—ranging from data storage and electric motors to sensors and spin-based energy devices—to solve their problems with predictive tools to design materials that maintain performance in changing conditions, especially at elevated temperatures.
Why This Matters Now: The Industry Impact
These works are interesting for the fields of Spintronics and Spin-Caloritronics.
The global spintronics market is expected to reach USD 23.8 billion by 2031, growing at a CAGR of 5.3% (Transparency Market Research, 2023).
Applications span:
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Magnetic memory (MRAM) and sensors in automotive and consumer electronics
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High-frequency signal processing and quantum computing
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Industrial automation and IoT
Industrial magnetic components often operate in non-equilibrium conditions with temperatures exceeding 600 K. Standard models fail to capture thermal degradation, noise, and instability—especially as device sizes shrink.
Our research offers a simulation-ready, physically grounded method to:
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Predict performance loss at high T
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Design materials that generate spin without current
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Tune magnetic stiffness for precision control
By incorporating these effects directly into first-principles models, we’re building a bridge between academic theory and industrial materials optimization.
1. How Spin and Lattice Scattering Shape Electronic Transport
In our first study, we calculated spin-dependent Seebeck coefficients (SDSE) from first principles using both the Boltzmann transport equation and variational methods. This quantity tells us how a temperature gradient can generate not only an electrical current—but a pure spin current, a crucial resource in spintronic devices.
Key Takeaways:
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Magnon scattering dominates resistivity below the Curie temperature (Tc), while phonon scattering dominates above it.
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Seebeck coefficients are sensitive to the energy dependence of scattering processes. Unlike resistivity, they cannot be understood using simple approximations.
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Our calculations suggest that in Permalloy, thermal gradients can produce pure spin currents of several μV/K, particularly at high temperatures .
This provides a new design lever for spin current injectors, avoiding electrical noise.
2. How Heat Changes Magnetism
In our second work , we focused on how phonons renormalize magnetic exchange interactions, modifying the spin wave (SW) dispersion and ultimately the Curie temperature (Tc) of magnetic materials. This coupling—known as magnon-phonon coupling (MPC)—is fundamental to thermal spin control, yet often neglected in modeling.
What We Found:
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In Permalloy, phonons significantly reduce near-neighbor magnetic exchange but increase long-range interactions, leading to a nonmonotonic behavior in the SW spectrum.
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By accounting for both lattice temperature (Tp) and spin temperature (Tm), we showed that the Curie temperature of Permalloy increases from 656 K (standard model) to 844 K with our MPC-enhanced model—matching experimental values .
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Our approach helps explain discrepancies between Bloch’s law predictions and actual experimental stiffness measurements in spintronic materials.
If you’re a researcher or R&D leader working on next-generation magnetic materials or spin-caloritronics, I’d be happy to connect.