Interfacial Fe segregation and its influence on magnetic properties of CoFeB/MgFeO multilayers

TL;DR

This study reveals that Fe segregation at the interface of CoFeB/MgFeO multilayers enhances perpendicular magnetic anisotropy and reduces magnetic damping, offering potential improvements for magnetic device performance.

Contribution

It demonstrates how Fe segregation influences magnetic properties and shows that inserting an ultrathin MgO layer further enhances these effects.

Findings

Over 2-fold increase in PMA energy density compared to CoFeB/MgO.

Fe segregates to form ferromagnetic metal at the interface.

Magnetic damping is significantly reduced in CoFeB/MgFeO multilayers.

Abstract

We investigated the effect of Fe segregated from partially Fe-substituted MgO (MgFeO) on the magnetic properties of CoFeB/MgFeO multilayers. X-ray photoelectron spectroscopy (XPS) as well as magnetic measurements revealed that the segregated Fe was reduced to metal and exhibited ferromagnetism at the CoFeB/MgFeO interface. The CoFeB/MgFeO multilayer showed more than 2-fold enhancement in perpendicular magnetic anisotropy (PMA) energy density compared with a standard CoFeB/MgO multilayer. The PMA energy density was further enhanced by inserting an ultrathin MgO layer in between CoFeB and MgFeO layers. Ferromagnetic resonance measurement also revealed a remarkable reduction of magnetic damping in the CoFeB/MgFeO multilayers.