  We investigate the effect of a unidirectional quenched random field on the
anisotropic quantum spin-1/2 $XY$ model, which magnetizes spontaneously in the
absence of the random field. We adopt mean-field approach to show that
spontaneous magnetization persists even in the presence of this random field
but the magnitude of magnetization gets suppressed due to disorder, and the
system magnetizes in the directions parallel and transverse to the random
field. Our results are obtained by analytical calculations within perturbative
framework and by numerical simulations. Interestingly, we show that it is
possible to enhance a component of the magnetization in presence of the
disorder field provided we apply an additional constant field in the $XY$
plane. Moreover, we derive generalized expressions for the critical temperature
and the scalings of the magnetization near the critical point for the $XY$ spin
system with arbitrary fixed quantum spin angular momentum.
