Shaping nanoscale magnetic domain memory in exchange-coupled ferromagnets by field cooling

TL;DR

This study uses coherent x-ray magnetic scattering to investigate nanoscale magnetic domain memory in exchange-coupled ferromagnetic films, revealing how cooling conditions influence the extent of magnetic domain repeatability.

Contribution

It demonstrates how field cooling conditions control magnetic domain memory in exchange-coupled ferromagnets at the nanoscale.

Findings

MDM can reach up to 100% in certain cooling conditions.

Cooling under moderate fields results in high MDM across the magnetization loop.

Nearly saturating field cooling suppresses MDM except at nucleation and saturation points.

Abstract

The advance of magnetic nanotechnologies relies on detailed understanding of nanoscale magnetic mechanisms in materials. Magnetic domain memory (MDM), i.e., the tendency for magnetic domains to repeat the same pattern during field-cycling, is important to many technologies including magnetic recording developments. We show coherent x-ray magnetic scattering studies unveiling MDM in [Co/Pd]/IrMn films. When illuminated by coherent x-rays, the magnetic domains in the [Co/Pd] multilayer produce a speckle pattern unique to their specific nanoscale configuration. By cross-correlating such speckle patterns throughout the magnetization loop, we measure the MDM. When cooled below its blocking temperature, the film exhibits up to 100% MDM, induced by exchange-couplings with the IrMn layer. Furthermore, the degree of MDM drastically depends on cooling conditions. If the film is cooled under moderate fields, MDM is high throughout the entire magnetization loop. If the film is cooled under nearly saturating field, MDM vanishes, except at nucleation and saturation