Real time probing of magnetization switching in magnetic nanostructures

Time-resolved anisotropic magnetoresistance (AMR) measurements of the irreversible switching of the magnetization were performed on isolated Ni nanowires. The magnetization reversal was triggered by injection of high current densities in a static magnetic field. The detection was achieved by means of a Wheatstone bridge with a 1 GHz bandwidth. Time-resolved switching was obtained in single shot measurements. Nanowires with diameter of about 100 nm that present a uniform rotation in the reversible regime detected in quasistatic AMR measurements are found to have switching in about 14 ns. This value can be accounted for in the framework of an uniform rotation model with value of the Gilbert damping coefficient of 0.005-0.01. Nanowires with larger diameters (typ. 200 nm) that manifest inhomogeneous magnetization in quasistatic AMR measurements have a switching time of about 37 ns.