Reversal studies on sub-micron CoCr thin films by AHE analysis

Abstract

In this study three CoCr thin films, prepared under different deposition conditions, are investigated. They have values for the coercivity ( H c) of 11, 90 and 170 kA/m, respectively. The anomalous Hall effect (AHE) has been used to record the hysteresis curves of specially prepared sub-micron Hall crosses. With this very sensitive technique the hysteresis loops were recorded of samples with Hall cross dimensions as small as 0.3 × 0.3 μm 2. The AHE loops of the samples, with less than 60 columns, show different ‘meso-magnetic’ properties. Only the sample with H c⊥ = 90 kA/m shows large steps in the curves above the noise level. The largest steps correspond with the reversal of one column. In this case the number of steps was 5 times the number of columns. From these measurements we conclude that the basic switching unit is smaller than one column. Furthermore the AHE results confirm that the low and the high coercive films reverses by domain wall motion and rotation respectively. The sample with H c = 90 kA/m switches with a combination of these two reversal mechanisms.