A Novel Effect of Electron Spin Resonance on Electrical Resistivity

TL;DR

This paper predicts a new resistivity effect caused by electron spin resonance in magnetic materials, where resonant AC fields induce additional momentum relaxation via spin fluctuations, extending classical magnetoresistance concepts.

Contribution

It introduces a novel mechanism of resistivity involving ESR-induced spin fluctuation excitations, extending Einstein's theory to near-equilibrium spin systems.

Findings

Predicted an order of magnitude increase in resistivity due to ESR effects.

Extended Einstein's derivation to include spin fluctuation excitations.

Proposed a new channel of momentum relaxation in magnetic materials.

Abstract

We extend the well known phenomenon of magnetoresistance (extra resistivity of materials in transverse magnetic field) to a new and unexplored regime where in addition to a transverse magnetic field, a transverse AC field of resonant frequency is also applied. In a magnetic field, electron spin levels are Zeeman split. In a resonant AC field, we uncover a new channel of momentum relaxation in which electrons in upper Zeeman level can deexcite to lower Zeeman level by generating spin fluctuation excitation in the lattice (similar to what happens in Electron Spin Resonance (ESR) spectroscopy). An additional resistivity due to this novel mechanism is predicted in which momentum randomization of Zeeman split electrons happen via bosonic excitations (spin fluctuations). An order of magnitude of this additional resistivity is calculated. The whole work is based upon an extension of Einstein's derivation of equilibrium Planckian formula to near equilibrium systems.