Magneto-optical Kerr effect (MOKE) measurements with uniform laser profiles

The probability distribution of the amplitude DeltaM of Barkhausen jumps during magnetization reversal in thin films can be measured with optical techniques since each jump produces a variation DeltaI of the laser beam intensity used to probe magnetization. Here we present a theoretical model which demonstrates that no distortion takes place if P(DeltaM) is a power law P(DeltaM)=DeltaM^(-alpha) with alpha >= 1.0. This prediction has been experimentally confirmed by measuring P(DeltaI) in the same experimental conditions but in two different ways: first with a Gaussian and then with a constant intensity laser profile. In both cases the same power-law distribution has been observed with alpha=1.