XMCD studies of thin Co films on BaTiO$_3$

TL;DR

This study investigates how the magnetic properties of cobalt thin films on BaTiO3 change with thickness, revealing an abrupt onset of magnetism around 9-10 Å due to island growth and coalescence.

Contribution

It provides detailed XMCD analysis of cobalt films on BaTiO3, identifying the critical thickness for magnetism onset and ruling out dead layers, which advances understanding of magnetic behavior in ferroelectric/metal interfaces.

Findings

Magnetic moments determined via XMCD sum rules.

Abrupt magnetism onset at 9-10 Å thickness.

No evidence of magnetically dead layers.

Abstract

Different layer thicknesses of Cobalt ranging from 2.6 {\AA} (1.5 ML) up to 55 {\AA} (30.5 ML) deposited on ferroelectric BaTiO$_3$ have been studied regarding their magnetic behavior. The layers have been characterized using XMCD spectroscopy at remanent magnetization. After careful data analysis the magnetic moments of the Cobalt could be determined using the sum rule formalism. There is a sudden and abrupt onset in magnetism starting at thicknesses of 9 {\AA} (5 ML) of Cobalt for measurements at 120 K and of 10 {\AA} (5.5 ML) if measured at room temperature. Initial island growth and subsequent coalescence of Co on BaTiO$_3$ is suggested to explain the sudden onset. In that context, no magnetically dead layers are observed.