Sub-nano tesla resolution differential magnetic field sensor utilizing asymmetrical magnetoimpedance in multilayer films

Asymmetrical magnetoimpedance (AMI) in multilayer thin films with cross anisotropy has been used for the development of a low noise, sensitive and quick response miniature magnetic sensor. The sensor is driven by a sinusoidal current of 90 MHz biased with a dc current. For an AMI film element of dimensions 5 mm long, 40 /spl mu/m wide, and having an anisotropy angle of 45/spl deg/, the field detection resolution is in the order of 1 /spl mu/ Oe for both ac and dc fields of magnitude 1 Oe. The maximum response speed is in the order of 1 MHz.