Current Fluctuations Driven by Ferromagnetic and Antiferromagnetic Resonance

TL;DR

This paper develops a generalized scattering theory to analyze current fluctuations driven by spin precession in ferromagnetic and antiferromagnetic materials, highlighting easier detection of antiferromagnetic resonance via shot noise.

Contribution

It extends existing models to include antiferromagnets and multiterminal devices, providing a comprehensive framework for studying current fluctuations in spintronic junctions.

Findings

Antiferromagnetic resonance is easier to detect via shot noise than ferromagnetic resonance.

Higher energy scales in antiferromagnets make their resonance signals more prominent.

The theory applies to various junction types, including ballistic and disordered contacts.

Abstract

We consider electron transport in ferromagnets or antiferromagnets sandwiched between metals. When spins in the magnetic materials precess, they emit currents into the surrounding conductors. Generally, adiabatic pumping in mesoscopic systems also enhances current fluctuations. We generalize the description of current fluctuations driven by spin dynamics in three ways using scattering theory. First, our theory describes a general junction with any given electron scattering properties. Second, we consider antiferromagnets as well as ferromagnets. Third, we treat multiterminal devices. Using shot noise-induced current fluctuations to reveal antiferromagnetic resonance appears to be easier than using them to reveal ferromagnetic resonance. The origin of this result is that the associated energies are much higher as compared to the thermal energy. The thermal energy governs the Johnson-Nyquist that is independent of the spin dynamics. We give results for various junctions, such as ballistic and disordered contacts. Finally, we discuss experimental consequences.