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.
@article{arxiv.0907.3286,
title = {Current Driven tri-stable Resistance States in Magnetic Point Contacts},
author = {I. K. Yanson and V. V. Fisun and Yu. G. Naidyuk and O. P. Balkashin and L. Yu. Triputen and A. Konovalenko and V. Korenivski},
journal= {arXiv preprint arXiv:0907.3286},
year = {2010}
}
Comments
4 pages, 5 Figs. accepted for publ. in J. Phys.: Cond. Mat., for additional exp. data see also: arXiv:0907.2027