Imaging Magnetization Structure and Dynamics in Ultrathin YIG/Pt Bilayers with High Sensitivity Using the Time-Resolved Longitudinal Spin Seebeck Effect

TL;DR

This paper introduces a highly sensitive, time-resolved magnetic imaging technique using the spin Seebeck effect to visualize magnetization structures and dynamics in ultrathin YIG/Pt bilayers with sub-micron spatial resolution.

Contribution

The study develops a novel TRLSSE microscopy method for imaging static and dynamic magnetization in ultrathin YIG/Pt bilayers with high temporal and spatial resolution.

Findings

Achieved sub-100 ps time resolution in magnetization detection.

Imaged static magnetic structures and GHz dynamics.

Sensitivity to magnetic orientation below 0.3°/√Hz.

Abstract

We demonstrate an instrument for time-resolved magnetic imaging that is highly sensitive to the in-plane magnetization state and dynamics of thin-film bilayers of yttrium iron garnet (Y3Fe5O12,YIG)/Pt: the time-resolved longitudinal spin Seebeck (TRLSSE) effect microscope. We detect the local, in-plane magnetic orientation within the YIG by focusing a picosecond laser to generate thermally-driven spin current from the YIG into the Pt by the spin Seebeck effect, and then use the inverse spin Hall effect in the Pt to transduce this spin current to an output voltage. To establish the time resolution of TRLSSE, we show that pulsed optical heating of patterned YIG (20 nm)/Pt(6 nm)/Ru (2 nm) wires generates a magnetization-dependent voltage pulse of less than 100 ps. We demonstrate TRLSSE microscopy to image both static magnetic structure and gigahertz-frequency magnetic resonance dynamics with sub-micron spatial resolution and a sensitivity to magnetic orientation below 0.3$^{\circ}/\sqrt{\text{Hz}}$ in ultrathin YIG.