Photocarrier Transport of Ferroelectric Photovoltaic Thin Films Detected by the Magnetic Dynamics of Adjacent Ferromagnetic Layers

TL;DR

This study uses time-resolved x-ray magnetic circular dichroism to observe how photocarriers in ferroelectric/ferromagnetic heterostructures influence magnetization dynamics, revealing insights into optical control of magnetization.

Contribution

It introduces a novel method to detect photocarrier transport in ferroelectric photovoltaic thin films via magnetic dynamics of adjacent layers.

Findings

Photocarrier transport affects magnetization decay times.

Decay time varies with ferroelectric polarization direction.

Photocarriers influence magnetization within ~100 ps.

Abstract

We have observed photocarrier transport behaviors in BiFeO$_3$/La$_{1-x}$Sr$_x$MnO$_3$~(BFO/LSMO) heterostructures by using time-resolved synchrotron x-ray magnetic circular dichroism in reflectivity. The magnetization of LSMO layers was used as a probe of photo-induced carrier dynamics in the photovoltaic BFO layers. During the photo-induced demagnetization process, the decay time of LSMO~($x$=0.2) magnetization strongly depends on the ferroelectric polarization direction of the BFO layer. The variation of decay time should be attributed to the different sign of accumulated photocarriers at the BFO/LSMO interface induced by the photovoltaic effect of the BFO layer. The photocarriers can reach the BFO/LSMO interface and influence the magnetization distribution in the LSMO layers within the timescale of $\sim$100~ps. Our results provide a novel strategy to investigate carrier dynamics and mechanisms of optical control of magnetization in thin film heterostructures.