Hysteretic magnetoresistance in nanowire devices due to stray fields induced by micromagnets

TL;DR

This paper investigates how stray magnetic fields from micromagnets induce hysteretic magnetoresistance in InSb nanowires, revealing effects similar to ferromagnetic contacts and suggesting potential applications in Majorana circuits.

Contribution

It demonstrates the impact of stray fields from micromagnets on nanowire magnetoresistance and provides micromagnetic simulations aligning with experimental observations.

Findings

Stray fields are in the tens of millitesla range.

Hysteretic magnetoresistance depends on micromagnet magnetization switching.

Stray field effects mimic those of ferromagnetic contacts.

Abstract

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.