  In this article we demonstrate the injection locking of recently demonstrated
spintronic feedback nano oscillator to microwave magnetic fields at integers as
well fractional multiples of its auto oscillation frequency. Feedback
oscillators have delay as a new degree of freedom which is absent for
spin-transfer torque based oscillators, which gives rise to side peaks along
with a main peak. We show that it is also possible to lock the oscillator on
its side band peaks, which opens a new avenue to phase locked oscillators with
large frequency differences. We observe that for low driving fields, side band
locking improves the quality factor of the main peak, whereas for higher
driving fields the main peak is suppressed. Further, measurements at two field
angles provide some insight into the role of symmetry of oscillation orbit in
determining the fractional locking.
