• Journal of Magnetics
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• 제14권4호
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• pp.147-149
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• 2009

We report the exchange bias in antiferromagnet/ferrimagnet $Cr_2O_3/Fe_3O_4$ core/shell nanoparticles. The magnetic field hysteresis curve for $Cr_2O_3/Fe_3O_4$ nanoparticles after field-cooling (FC) clearly showed both horizontal ($H_{EB}{\sim}$610 Oe) and vertical (${\Delta}M{\sim}$5.6 emu/g) shifts at 5 K. These shifts disappeared as the temperature increased toward the Neel temperature of $Cr_2O_3\;(T_N{\sim}$307 K). The $H_{EB}\;and\;{\Delta}M$ values were sharply decreased between the $1^{st}\;and\;the\;2^{nd}$ magnetic field cycles, and then slowly decreased with further cycling. These results are discussed in terms of the formation of single domains with pinned, uncompensated, antiferromagnetic spin and their evolution into multi-domains with cycling.

• Journal of Magnetics
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• 제16권4호
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• pp.323-327
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• 2011

By means of Monte Carlo simulation, we investigate the effects of interface roughness and temperature on the exchange bias and coercivity in ferromagnetic (FM)/antiferromagnetic (AFM) bilayers. Both exchange bias and coercivity are strongly dependent on interface roughness. For a perfect uncompensated interface a domain wall is formed in the AFM system during FM reversal, which results in a very small exchange bias. However, a finite interface roughness leads to a finite value of the exchange bias due to the existence of pinned spins at the AFM surface adjacent to the mixed interface. It is observed that the exchange bias decreases with increasing temperature, consistent with the experimental results. It is also observed that a bump in coercivity occurs around the blocking temperature.