Revealing Optically Induced Magnetization in SrTiO$_3$ using Optically Coupled SQUID Magnetometry and Magnetic Circular Dichroism

TL;DR

This study demonstrates that circularly polarized sub-bandgap light can induce long-lived, optically addressable magnetization in SrTiO$_{3- ext{δ}}$, enabling optical magnetic memory, with the magnetization arising from oxygen-vacancy complexes rather than collective order.

Contribution

First demonstration of optically induced, long-lived magnetization in SrTiO$_{3- ext{δ}}$ using coupled SQUID and magnetic circular dichroism techniques, revealing potential for optical magnetic memory.

Findings

Magnetization induced by circularly polarized light lasts hours.

Magnetization can be written and read optically.

Magnetization originates from oxygen-vacancy complexes.

Abstract

In this work, we study the time- and temperature-dependence of optically induced magnetization in bulk crystals of slightly oxygen-deficient SrTiO$_{3-\delta}$ using an optically coupled SQUID magnetometer. We find that a weak ($\sim$5$\times$10$^{-7}$~emu) but extremely long-lived (hours) magnetic moment can be induced in SrTiO$_{3-\delta}$ at zero magnetic field by circular-polarized sub-bandgap light. We utilize this effect to demonstrate that SrTiO$_{3-\delta}$ crystals can be used as an optically addressable magnetic memory by writing and subsequently reading magnetic patterns with light. The induced magnetization is consistent with that of a polarized ensemble of independent oxygen-vacancy-related complexes, rather than from collective or long-range magnetic order.