  The exchange bias (EB) effect has been observed in magnetic
Bi$_{0.9}$Gd$_{0.1}$Fe$_{0.9}$Ti$_{0.1}$O$_3$ nanoparticles. The influence of
magnetic field cooling on the exchange bias effect has also been investigated.
The magnitude of the exchange bias field ($H_{EB}$) increases with the cooling
magnetic field, showing that the strength of the exchange bias effect is
tunable by the field cooling. The $H_{EB}$ values are also found to be
dependent on the temperature. This magnetically tunable exchange bias obtained
at temperatures up to 250 K in Bi$_{0.9}$Gd$_{0.1}$Fe$_{0.9}$Ti$_{0.1}$O$_3$
nanoparticles may be worthwhile for potential applications.
