Exchange-bias stabilization of the magnetic nanoparticles in a granular alloy grown by reactive sputtering

• Published in: Applied physics letters Vol. 86; no. 17; pp. 172503 - 172503-3
• Main Authors: Riveiro, J. M., De Toro, J. A., Andrés, J. P., González, J. A., Muñoz, T., Goff, J. P.
• Format: Journal Article
• Language: English
• Published: American Institute of Physics 25-04-2005
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.1921353

The superparamagnetic blocking temperature of a series of granular
Co
22
Ag
78
alloys grown by reactive sputtering under oxygen atmosphere exhibits a minimum when plotted as a function of the oxygen pressure. The magnetic stabilization observed above this minimum is found to arise from the exchange-bias between the Co core and a CoO shell, which appears to be spin disordered. The initial decrease in the blocking temperature at low oxygen pressures is mainly attributed to the inhibition of RKKY-like interactions by the formation of an insulating oxide layer, too thin to give rise to exchange bias, around the ferromagnetic cores.