Current Driven tri-stable Resistance States in Magnetic Point Contacts

TL;DR

This paper reports the discovery of tri-stable resistance states in magnetic point contacts, attributed to surface spin configurations influenced by spin transfer torques, expanding understanding of nanoscale magnetic phenomena.

Contribution

It introduces the observation of tri-stable resistance states in magnetic point contacts and interprets them as surface spin-valve and vortex states, highlighting the role of interface spin structures.

Findings

Hysteresis observed in resistance versus bias current and magnetic field.

Identification of tri-stable resistance states beyond traditional bi-stable states.

Surface spin states dominate spin transfer effects at the nanoscale.

Abstract

Point contacts between normal and ferromagnetic metals are investigated using magneto-resistance and transport spectroscopy measurements combined with micromagnetic simulations. Pronounced hysteresis in the point-contact resistance versus both bias current and external magnetic field are observed. It is found that such hysteretic resistance can exhibit, in addition to bi-stable resistance states found in ordinary spin valves, tri-stable resistance states with a middle resistance level. We interpret these observation in terms of surface spin-valve and spin-vortex states, originating from a substantially modified spin structure at the ferromagnetic interface in contact core. We argue that these surface spin states, subject to a weakened exchange interaction, dominate the effects of spin transfer torques on the nanometer scale.