Evidence for the collapse of short-range magnetic order in CoO at the Néel temperature

¹ IOM-CNR Istituto Officina dei Materiali del CNR, Area Science Park - Basovizza, Trieste, Italy, EU
² CNISM and Dipartimento di Fisica, Università Roma Tre - Rome, Italy, EU
³ Department of Physics and Astronomy and Laboratory of Surface Modification, Rutgers University Piscataway, NJ, US
⁴ Dipartimento di Fisica, Università di Roma Tor Vergata - Rome, Italy, EU
⁵ Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare - Frascati, Italy, EU

Received: 1 December 2010
Accepted: 24 March 2011

Abstract

Auger-photoelectron coincidence spectroscopy is used for investigating the electronic properties of a CoO thin film above and below the magnetic transition temperature (T_N). By using the dichroic effect in angle-resolved measurements, we identify and assign well-defined high-spin and low-spin structures in spite of the otherwise featureless Auger singles spectra, typically found for open-band systems. The disappearance of the dichroism for temperatures just above T_N indicates a collapse of the surface short-range magnetic order, presumably due to a strongly reduced exchange field in the surface compared to that in the bulk.