Off-diagonal impedance in amorphous wires and application to linear magnetic sensors

摘要

The magnetic-field behaviour of the off-diagonal impedance in Co-basedamorphous wires is investigated under the condition of sinusoidal (50 MHz) andpulsed (5 ns rising time) current excitations. For comparison, the fieldcharacteristics of the diagonal impedance are measured as well. In general,when an alternating current is applied to a magnetic wire the voltage signal isgenerated not only across the wire but also in the coil mounted on it. Thesevoltages are related with the diagonal and off-diagonal impedances,respectively. It is demonstrated that these impedances have a differentbehaviour as a function of axial magnetic field: the former is symmetrical andthe latter is antisymmetrical with a near linear portion within a certain fieldinterval. In the case of the off-diagonal response, the dc bias currenteliminating circular domains is necessary. The pulsed excitation that combinesboth high and low frequency harmonics produces the off-diagonal voltageresponse without additional bias current or field. This suits ideal for apractical sensor circuit design. The principles of operation of a linearmagnetic sensor based on C-MOS transistor circuit are discussed.