A new fundamental relationship between magnetism and spin dynamics has been uncovered, offering insights that could shape the future of spintronic and nanoelectronic devices. Researchers have derived and experimentally validated a formula linking a material’s magnetic permeability to the frequencies of its magnetic spin resonances. This discovery mirrors an 84-year-old relationship in electrical dynamics but reveals a striking difference: while the dielectric function depends on phonon frequencies quadratically, the newly established magnetic relation shows a linear dependence on spin resonance frequencies.
More details on this discovery can be found in the original publication: New Fundamental Magnetic Law Uncovered.
The finding emerges from an interplay between theory and high-precision experiments. Researchers worked with gallium nitride doped with paramagnetic iron, using techniques like Mueller-matrix ellipsometry and superconducting quantum interference device (SQUID) measurements to extract key magnetic parameters. The derived formula reflects a fundamental distinction between spin precession and ionic motion, which affects how magnetic permeability behaves under dynamic conditions.
A core component of this work is its reliance on Felix Bloch’s 1946 spin precession theory. By applying Bloch’s framework, the team quantified spin contributions and determined precession directions, aligning experimental and theoretical insights. The methodology demonstrated here may significantly impact magneto-optical characterization techniques, particularly for materials like antiferromagnets and altermagnets, which hold promise for high-speed, energy-efficient computing.
One of the most practical aspects of this study is that its approach does not necessarily require high-frequency optical techniques. In many cases, conventional reflectivity and transmission measurements may suffice, provided the material’s magnetic dipoles are strong enough. This opens up new avenues for designing and characterizing spintronic materials without the need for ultrafine spectral resolution.
As interest in spin-based electronics grows, understanding the fundamental connections between magnetic permeability and spin resonance could provide a new foundation for developing devices that operate at gigahertz frequencies. This research not only enhances fundamental knowledge but also lays the groundwork for more efficient methods to analyze and engineer next-generation magnetic materials.