Barkhausen noise in variable thickness amorphous finemet films

We measured the statistical properties of Barkhausen noise in finemet films with nominal composition Fe73.5Cu1Nb3Si22.5B4 and variable thickness between 25 and 1000nm. Films have been sputtered on glass substrates and their structure is amorphous. The critical exponents of the power-law distributions for the jumps amplitude show a remarkable stability over the whole thickness range, whereas the other macroscopic magnetic properties undergo strong variations. The value of the critical exponent is about 0.8 between 50 and 500nm with a small increase up to 1.0 at 1000nm. These values are similar to those observed with the same experimental technique in other two-dimensional (2D) systems, but definitely smaller with respect to the values observed in truly three-dimensional (3D) systems. Our data therefore indicate that, in the investigated thickness range, the behavior remains typical of 2D systems. The small increase of the critical exponent at 1000nm might be an indication of a starting transition toward a 3D behavior.