X-ray microscopy and spectroscopy insights of organic spin-valve

One recent focus in spintronics is the observation of giant magnetoresistance (GMR) in organic spin-valve (OSV). Sandwiched by two ferromagnetic (FM) layers, organic semiconductor (OSC) was incorporated into the spin-valve structure to take advantage of its low spin-orbit interaction so that the coherence of spin-polarized carriers can be preserved over an extended time. The observation of GMR in OSV is thus a promising result suggesting spins have indeed travelled through OSC. However, until now, the magnetoresistance (MR) ratio given by OSV remains to be relatively low and highly sensitive to temperature. Obviously, our understanding on OSV is far from complete, and there are unidentified effects hindering the transport of spins in OSV. In this report, we present the experimental evidences suggesting that the absence of room temperature GMR in OSV may be related to the diffusion of metal clusters from metallic top electrode into OSC layer. Our findings also offer a plausible explanation on why inserting an oxide layer between OSC and FM electrode can improve the MR ratio of OSV.