Nanoscale Magnetic Domain Memory

TL;DR

This paper reviews the phenomenon of nanoscale magnetic domain memory (MDM), detailing how it occurs in various magnetic materials and conditions, and how it can be controlled through cooling and material coupling techniques.

Contribution

It provides a comprehensive overview of MDM mechanisms, experimental observations, and control methods, highlighting new insights into nanoscale magnetic memory behavior.

Findings

MDM observed in rough Co/Pt multilayers due to defects

Achieving 100% MDM via exchange coupling with antiferromagnetic layers

MDM can be controlled by cooling field adjustments

Abstract

Magnetic domain memory (MDM) is the ability exhibited by certain magnetic materials to reproduce the exact same nanoscale magnetic domain pattern, even after it has been completely erased by an external magnetic field. In this chapter, we review the various circumstances under which this unusual phenomenon occurs. We explain how partial MDM was first observed in rough Co/Pt multilayers with perpendicular magnetization as a result of structural defects. We then show how 100 % MDM was achieved, even in smooth ferromagnetic films, by coupling Co/Pd multilayers to an antiferromagnetic IrMn template via exchange interactions. We describe how high MDM, extending through-out nearly the entirety of the magnetization process, is obtained when zero-field-cooling the material below its blocking temperature where exchange couplings occur. We also review the persistence of MDM through field cycling and while warming the material all the way up to the blocking temperature. Additionally, we discuss the spatial dependence of MDM, highlighting intriguing oscillatory behaviors suggesting magnetic correlations and rotational symmetries at the nanoscopic scales. Finally, we review the dependence of MDM on cooling conditions, revealing how MDM can be fully controlled, turned on and off, by adjusting the magnitude of the cooling field.