  We investigated effects of neutron-proton ($np$) pairing correlations
comprising isoscalar (IS) and isovector (IV) component on Gamow-Teller (GT)
transitions of $^{56, 58,62,64}$Ni by taking into account nuclear deformation
in a deformed Woods-Saxon mean field. Our GT calculations based on a deformed
Bardeen-Cooper-Schriffer (DBCS) approach have been performed within a deformed
quasi-particle random phase approximation (DQRPA) which explicitly includes the
deformation as well as all kinds of pairing correlations not only at the DBCS
but also at the DQRPA stage. Competition of these two effects, the deformation
and the IS spin-triplet and IV spin-singlet component of the $np$ pairing, is
shown to be significant for understanding the GT strength distributions of Ni
isotopes.
