  We theoretically examine a cross effect of magnetic field and charge current
on antiferromagnetic domain wall dynamics. Since antiferromagnetic materials
are largely insensitive to external magnetic fields in general, charge current
has been shown recently as an alternative and efficient way to manipulate
antiferromagnets. We find a new role of the magnetic field in the
antiferromagnetic dynamics that appears when it is combined with charge
current, demonstrating a domain wall motion in the presence of both field and
current. We show that a spatially-varying magnetic field can shift the
current-driven domain-wall velocity, depending on the domain-wall structure and
the direction of the field-gradient. Our result suggests a novel concept of
field-control of current-driven antiferromagnetic dynamics.
