Magneto-optical measurements of magnetization reversal in nanometer scale sputtered Fe thin films

We present a magneto-optical study of the magnetic behavior of sputtered iron films of various thickness ranging from 2 to 50 nm grown on a silicon substrate. First we calculate the reflection coefficients in the case of an homogeneous magneto-optical layer with in-plane magnetization. Then we describe a technique in which both in-plane magnetization components are detected. Because of the axial deposition procedure, iron films exhibit in-plane uniaxial anisotropy depending on the thickness of the layer. In particular, we show that, for 4 nm thickness, anistropy induced by slightly tilted columnar growth can be observed, whereas for larger thicknesses this in-plane anisotropy vanishes. Using an accurate acquisition system based upon a rapid analog-to-digital converter we measured the rapid magnetization reversal. The field sweep rate was varied between 100 Oe/s and 1 MOe/s. We interpret the observed dynamical effects in terms of wall movement and microdomain reversal.