Volume 77, Number 5, March 2007
Article Number 57006
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 22 February 2007
EPL, 77 (2007) 57006
DOI: 10.1209/0295-5075/77/57006

Exchange bias in granular CoO layers due to random magnetic anisotropy

M. Gruyters

Institut für Physik, Humboldt-Universität zu Berlin - Newtonstrasse 15, 12489 Berlin, Germany

received 9 October 2006; accepted in final form 19 January 2007; published March 2007
published online 22 February 2007

The structural and magnetic properties of granular CoO layers have been investigated by scanning tunneling microscopy (STM) and magnetization measurements. The CoO shows a strong exchange anisotropy which is attributed to an interaction between the antiferromagnetic order and uncompensated spins in the antiferromagnetic material. No appreciable amount of ferromagnetic material is needed to establish characteristic properties of exchange bias such as the shift of the magnetic hysteresis loop. A new approach to the problem of exchange anisotropy is suggested which is based on random magnetic anisotropy of CoO nanoparticles.

75.70.-i - Magnetic properties of thin films, surfaces, and interfaces.
75.50.Ee - Antiferromagnetics.
75.50.Lk - Spin glasses and other random magnets.

© Europhysics Letters Association 2007