Magnetic field control of the spin Seebeck effect

TL;DR

This study investigates how applied magnetic fields suppress the longitudinal spin Seebeck effect by altering magnon frequency spectra, using numerical simulations and experimental data to reveal the underlying mechanisms.

Contribution

It introduces a detailed atomistic spin model simulation to explain the magnetic field dependence of the spin Seebeck effect, aligning well with experimental observations.

Findings

Magnon accumulation decreases with increasing magnetic field.

Magnetic fields suppress parts of the magnon frequency spectrum.

The model accurately reproduces experimental data on YIG thin films.

Abstract

The origin of the suppression of the longitudinal spin Seebeck effect by applied magnetic fields is studied. We perform numerical simulations of the stochastic Landau-Lifshitz-Gilbert equation of motion for an atomistic spin model and calculate the magnon accumulation in linear temperature gradients for different strengths of applied magnetic fields and different length scales of the temperature gradient. We observe a decrease of the magnon accumulation with increasing magnetic field and we reveal that the origin of this effect is a field dependent change of the frequency distribution of the propagating magnons. With increasing field the magnonic spin currents are reduced due to a suppression of parts of the frequency spectrum. By comparison with measurements of the magnetic field dependent longitudinal spin Seebeck effect in YIG thin films with various thicknesses, we find that our model describes the experimental data very well, demonstrating the importance of this effect for experimental systems.