Difference between Blocking and Néel Temperatures in the Exchange Biased Fe3O4/CoO System
The blocking temperature TB has been determined as a function of the antiferromagnetic layer thickness in the Fe3O4/CoO exchange biased system. For CoO layers thinner than 50 Å, TB is reduced below the Néel temperature TN of bulk CoO (291 K), independent of crystallographic orientation or film substrate ( α−Al2O3, SrTiO3, and MgO). Neutron diffraction studies show that TB does not track the CoO ordering temperature and, hence, that this reduction in TB does not arise from finite-size scaling. Instead, the ordering temperature of the CoO layers is enhanced above the bulk TN for layer thicknesses ≲100Å due to the proximity of magnetic Fe3O4 layers.
van der Zaag, P.J., Y. Ijiri, A. Borchers, et al. 2000. "Difference between Blocking and Néel Temperatures in the Exchange Biased Fe3O4/CoO System." Physical Review Letters 84(26): 6102-6105.
American Physical Society
Physical Review Letters
Physics and Astronomy