Point-contacts (PC) offer a simple way to create high current densities, 10^9 A/cm^2 and beyond, without substantial Joule heating. We have shown recently (Nano Letters, 7 (2007) 927) that conductivity of nanosized PCs between a normal and ferromagnetic metals exhibits bi-stable hysteretic states versus both bias current and external magnetic field - the effect typical for spin-valve structures. Here we report that apart from the bi-stable state a third intermediate-resistance state is occasionally observed. We interpret this state as due to a spin-vortex in the PC, nucleated either by Oersted field of the bias current and/or by the circular geometry of PC. The observed three-level-states in the PC conductivity testify that the interface spins are both weakly coupled to the spins in the bulk and have depressed exchange interaction within the surface layer.
@article{arxiv.0907.2027,
title = {Vortex-like state observed in ferromagnetic contacts},
author = {I. K. Yanson and Yu. G. Naidyuk and V. V. Fisun and O. P. Balkashin and L. Yu. Triputen and A. Konovalenko and V. Korenivski},
journal= {arXiv preprint arXiv:0907.2027},
year = {2010}
}
Comments
4 pgs., 4 figs. submitted to ICM-09 (July 26-21, Karlsruhe) V2: corrected typos, accepted for publication in J. Phys.: Conf. Series