William F. Witcraft

Effect of magnetic anisotropy on signal and noise of NiFe magnetoresistive sensor

The effect of magnetic anisotropy field (K/sub K/) on the signal and noise characteristics of NiFe magnetoresistive (MR) sensor has been studied. Lowering the anisotropy field of the thin NiFe films not only increases the sensitivity of the MR sensors but also induces higher noise. The experimental results show that the sensitivity is inversely proportional to the anisotropy field H/sub K/, while the noise is inversely proportional to the (H/sub K/)/sup 2/. The increased sensitivity of the MR sensor is attributed to the increased susceptibility of the sample films associated with lowering the anisotropy field. The noise level of the sensor is found to be increased with decreased anisotropy field, which can be explained by the induced instability of the magnetic domain structure of the NiFe films due to the anisotropy field decrease.