  We observe an unusual tunneling magnetoresistance (TMR) phenomenon in a
composite of La$_{2/3}$Sr$_{1/3}$MnO$_{3}$ with CoFe$_{2}$O$_{4}$ where the TMR
versus applied magnetic field loop suggests a "negative coercive field".
Tracing its origin back to a "dipolar-biasing" of La$_{2/3}$Sr$_{1/3}$MnO$_{3}$
by CoFe$_{2}$O$_{4}$, we show that the TMR of even a single composite can be
tuned continuously so that the resistance peak or the highest sensitivity of
the TMR can be positioned anywhere on the magnetic field axis with a suitable
magnetic history of the sample. This phenomenon of an unprecedented tunability
of the TMR should be present in general in all such composites.
