  A precondition for the radio emission of pulsars is the existence of strong,
small-scale magnetic field structures (`magnetic spots') in the polar cap
region. Their creation can proceed via crustal Hall drift out of two
qualitatively and quantitatively different initial magnetic field
configurations: a field confined completely to the crust and another which
penetrates the whole star. The aim of this study is to explore whether these
magnetic structures in the crust can deform the star sufficiently to make it an
observable source of gravitational waves. We model the evolution of these field
configurations, which can develop, within $\sim 10^4$ -- $10^5$ yr, magnetic
spots with local surface field strengths $\sim 10^{14}$ G maintained over
$\gtrsim 10^6$ yr. Deformations caused by the magnetic forces are calculated.
We show that, under favourable initial conditions, a star undergoing crustal
Hall drift can have ellipticity $\epsilon\sim 10^{-6}$, even with sub-magnetar
polar field strengths, after $\sim 10^5$ yr. A pulsar rotating at $\sim 10^2$
Hz with such $\epsilon$ is a promising gravitational-wave source candidate.
Since such large deformations can be caused only by a particular magnetic field
configuration that penetrates the whole star and whose maximum magnetic energy
is concentrated in the outer core region, gravitational wave emission observed
from radio pulsars can thus inform us about the internal field structures of
young neutron stars.
