Direct observation of rotatable uncompensated spins in the exchange bias system Co/CoO-MgO

Chuannan Ge, Xiangang Wan*, Eric Pellegrin, Zhiwei Hu, S. Manuel Valvidares, Alessandro Barla, Wen I. Liang, Ying-hao Chu, Wenqin Zou, Youwei Du

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

We have observed a large exchange bias field H E ≈ 2460 Oe and a large coercive field H C ≈ 6200 Oe at T = 2 K for Co/CoO core-shell nanoparticles (∼4 nm diameter Co metal core and CoO shell with ∼1 nm thickness) embedded in a non-magnetic MgO matrix. Our results are in sharp contrast to the small exchange bias and coercive field in the case of a non-magnetic Al 2 O 3 or C matrix materials reported in previous studies. Using soft X-ray magnetic circular dichroism at the Co-L 2,3 edge, we have observed a ferromagnetic signal originating from the antiferromagnetic CoO shell. This gives direct evidence for the existence of rotatable interfacial uncompensated Co spins in the nominally antiferromagnetic CoO shell, thus supporting the uncompensated spin model as a microscopic description of the exchange bias mechanism.

Original languageEnglish
Pages (from-to)10236-10241
Number of pages6
JournalNanoscale
Volume5
Issue number21
DOIs
StatePublished - 7 Nov 2013

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