Probing the interface magnetism in the FeMn/NiFe exchange bias system using magnetic second harmonic generation

TL;DR

This study uses magnetic second harmonic generation to investigate interface magnetism in NiFe/FeMn bilayers, revealing the role of pinned uncompensated spins in exchange bias control.

Contribution

It demonstrates the application of SHMOKE to probe buried interface spins and links exchange bias to pinned uncompensated spins in the antiferromagnetic layer.

Findings

Reversible and irreversible uncompensated spins are present near the interface.

Exchange bias field correlates with pinned uncompensated spins.

SHMOKE hysteresis matches standard magnetometry results.

Abstract

Second harmonic generation magneto-optic Kerr effect (SHMOKE) experiments, sensitive to buried interfaces, were performed on a polycrystalline NiFe/FeMn bilayer in which areas with different exchange bias fields were prepared using 5 KeV He ion irradiation. Both reversible and irreversible uncompensated spins are found in the antiferromagnetic layer close to the interface with the ferromagnetic layer. The SHMOKE hysteresis loop shows the same exchange bias field as obtained from standard magnetometry. We demonstrate that the exchange bias effect is controlled by pinned uncompensated spins in the antiferromagnetic layer.