  We study hysteretic magnetoresistance in InSb nanowires due to stray magnetic
fields from CoFe micromagnets. Devices without any ferromagnetic components
show that the magnetoresistance of InSb nanowires commonly exhibits either a
local maximum or local minimum at zero magnetic field. Switching of microstrip
magnetizations then results in positive or negative hysteretic dependence as
conductance maxima or minima shift with respect to the global external field.
Stray fields are found to be in the range of tens of millitesla, comparable to
the scale over which the nanowire magnetoresistance develops. We observe that
the stray field signal is similar to that obtained in devices with
ferromagnetic contacts (spin valves). We perform micromagnetic simulations
which are in reasonable agreement with the experiment. The use of locally
varying magnetic fields may bring new ideas for Majorana circuits in which
nanowire networks require control over field orientation at the nanoscale.
