Direct observation of non-Gaussian distribution of local magnetic properties in ferromagnetic thin films

Abstract

We report our experimental finding that magnetic properties of Co-based multilayer films are shown to exhibit their local variations far from the Gaussian (or Lorentzian) distribution which are usually assumed. The local variations of the coercivity and the field dependence $\ensuremath{\lambda}(=\ensuremath{-}\ensuremath{\partial}\mathrm{ln}\ensuremath{\tau}/\ensuremath{\partial}H)$ were determined from measurements of the hysteresis loop and the field-dependent switching time \ensuremath{\tau}, respectively, on spatially resolved local regions 400 nm in size by means of a magneto-optical microscope magnetometer. We show that the two local magnetic properties inversely correlate with each other and a thermally activated process takes place during magnetization reversal on a submicrometer scale in ferromagnetic thin films.