Exchange bias in GeMn nanocolumns: the role of surface oxidation

Samuel Tardif (1, 2) , Salia Cherifi (1) , M. Jamet (2) , T. Devillers (2) , A. Barski (2) , D. Schmitz (3) , N. Darowski (3) , P. Thakur (4) , J. C. Cezar (4) , N. B. Brookes (4) , R. Mattana (5) , Joel Cibert (6)

1 NEEL - MNM - Micro et NanoMagnétisme
2 INAC - Institut Nanosciences et Cryogénie
3 HZB - Helmholtz-Zentrum Berlin für Materialien und Energie GmbH = Helmholtz Centre Berlin for Materials and Energy = Centre Helmholtz de Berlin pour les matériaux et l'énergie
4 ESRF - European Synchrotron Radiation Facility
5 Laboratoire Albert Fert (ex-UMPhy Unité mixte de physique CNRS/Thales)
6 NEEL - NPSC - Nanophysique et Semiconducteurs

We report on the exchange biasing of self-assembled ferromagnetic GeMn nanocolumns by GeMn-oxide caps. The x-ray absorption spectroscopy analysis of this surface oxide shows a multiplet fine structure that is typical of the Mn2+ valence state in MnO. A magnetization hysteresis shift |HE|~100 Oe and a coercivity enhancement of about 70 Oe have been obtained upon cooling (300-5 K) in a magnetic field as low as 0.25 T. This exchange bias is attributed to the interface coupling between the ferromagnetic nanocolumns and the antiferromagnetic MnO-like caps. The effect enhancement is achieved by depositing a MnO layer on the GeMn nanocolumns.

Mots clés: XMCD; Exchange bias; MnO; GeMn

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Samuel Tardif, Salia Cherifi, M. Jamet, T. Devillers, A. Barski, et al.. Exchange bias in GeMn nanocolumns: the role of surface oxidation. Applied Physics Letters, 2010, 97 (6), pp.062501. ⟨10.1063/1.3476343⟩. ⟨hal-00510381⟩