Dresden 2011 – wissenschaftliches Programm
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KR: Fachgruppe Kristallographie
KR 5: Poster Multiferroics (Joint Session of MA, DF, DS, KR, TT)
KR 5.81: Poster
Dienstag, 15. März 2011, 10:45–13:00, P2
Exchange bias due to surface-stabilized spin glass in Co33Fe67-CoFe2O4 core-shell nanoparticles — •Syed Rizwan Ali1, Ghulam Hassnain Jaffari2, Syed Khurshid Hasanain3, Gernot Güntherodt1, and Syed Ismat Shah2 — 1Physikalisches Institut (IIA), RWTH Aachen University, Aachen 52056, Germany — 2Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA — 3Department of Physics, Quaid-i-Azam University, Islamabad 45320, Pakistan
We investigate the magnetic and exchange bias (EB) properties of Co33Fe67CoFe2O4 (core-shell) nanoparticles [1]. Both dc magnetization and ac susceptibility measurements indicate the onset of a spin glass (SG) like transition at the freezing temperature of TF=175 K. The SG transition is also supported by the field dependence of TF following the well known Almeida-Thouless line, i.e. TF~H2/3. Moreover, the particles exhibit a large EB field, HEB=1357 Oe arising from the core-shell (ferromagnetic-SG) coupling. The unusually high TF and large EB effects are attributed to several factors including the thickness of the amorphous oxide shell and large values of the exchange and anisotropy constants associated with the CoFe2O4 shell.
[1] G. H. Jaffari, S. R. Ali, S. K. Hasanain, G. Güntherodt, and S. I. Shah, J. Appl. Phys. vol. 108, pp. 063921 (2010).