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

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.

Integrating micromagnets and hybrid nanowires for topological quantum computing

“…The range of field where wide and narrow micromagnets are antiparallel is determined from separate SQUID measurements to be between 15 and 20 mT, in agreement with Ref. [29], when reduced CoFe thickness is accounted for.…”

“…Among the limitations is the still limited strength of stray fields from micromagnets. In previous experiments the typical stray fields are in the range of tens of milliTesla [29]. This is in principle sufficient to enter the topological regime in large g-factor semiconductor such as…”

“…The micromagnet widths are different to ensure different switching fields and to aid in the preparation of a desired mutual magnetization pattern [29]. The magnets are rotated at 45 degrees to aid magnetization through the hysteresis simulation.…”

“…For work that utilizes the Poisson Schrödinger equation to model MZMs in the 3D geometry of a single nanowire [26,37,38], where the use of 3D field profiles could give a batter picture of systems in future studies. Further work on implementing micromagnets for use in Majorana based devices [29]. There are several different proposed braiding schemes using nanowire-network junction devices [26,39], with options such as using local chemical potential changes [32] or flux gates [40].…”

Integrating micromagnets and hybrid nanowires for topological quantum computing

“…The micromagnet widths are different to ensure different switching fields and to aid in the preparation of a desired mutual magnetization pattern [27]. The magnets are rotated at 45 degrees to aid magnetization through the hysteresis simulation.…”