Mr sensors with selected resistances for the sensing and biasing layers

Abstract

A magnetoresistive sensor for detecting stored information from a magnetic medium and for providing an output voltage to auxiliary circuitry is disclosed. The magnetoresistive sensor includes a magnetoresistive magnetic layer formed from a magnetic material, the magnetic layer having a magnetization, a resistivity and a thickness. A resistance of the magnetic layer equals the resistivity of the layer divided by the thickness of the layer. The magnetic sensor also comprises a bias layer having a resistivity, a thickness and a saturation inductance. A resistance of the bias layer equals the resistivity of the layer divided by the thickness of the layer. The resistance of the bias layer is in parallel with the resistance of the magnetic layer. The saturation inductance of the bias layer helps to bias the magnetic layer from a rest position to a magnetized position. A spacer layer is positioned between the magnetic layer and the bias layer. The spacer layer has a resistivity and a thickness. A resistance of the spacer layer equals the resistivity of the layer divided by the thickness of the layer. The resistance of the spacer layer is in parallel with both the resistances of the magnetic layer and the bias layer. The parallel resistances of the bias layer and the spacer layer is at least twice as large as the resistance of the magnetic layer such that at least two-thirds of the current flows through the magnetic layer and at most one-third of the current flows through the combination of the bias layer and the spacer layer.