Spin Accumulation based deep MOKE Microscopy

TL;DR

This paper introduces a novel SA-MOKE microscopy technique that images magnetic thin-films beneath thick, opaque metallic layers by detecting transient spin-accumulations, overcoming optical limitations in traditional methods.

Contribution

The work presents a new spin-accumulation based MOKE method enabling magnetic imaging through thick metallic covers, expanding the applicability of magnetic microscopy.

Findings

Spin-accumulation signals decay length of 60 nm in Cu.

Detection of magnetic contrast through Cu layers up to hundreds of nm.

Method effective for imaging beneath opaque metallic layers.

Abstract

Magnetic imaging techniques are widespread critical tools used in fields such as magnetism, spintronics or even superconductivity. Among them, one of the most versatile methods is the magneto-optical Kerr effect. However, as soon as light is blocked from interacting with the magnetic layer, such as in deeply buried layers, optical techniques become ineffective. In this work, we present a spin-accumulation based magneto-optical Kerr effect (SA-MOKE) microscopy technique that enables imaging of a magnetic thin-films covered by thick and opaque metallic layers. The technique is based on the generation and detection of transient spin-accumulations that propagate through the thick metallic layer. These spin-accumulation signals are directly triggered and detected optically on the same side, lifting any substrate transparency requirements. The spin-accumulation signals detected on a Cu layer decay with a characteristic length of 60 nm, much longer than the 12 nm optical penetration depth, allowing for detection of magnetic contrast with Cu capping layers up to hundreds of nm. This method should enable magnetic imaging in a wide-range of experiments where the surface of interest is covered by electrodes.