Increased sensitivity in local probe of magnetic properties

摘要

An apparatus, system, and method for probing magnetic permeability of a material located a distance from the apparatus comprises a first hard ferromagnetic layer, a second hard ferromagnetic layer, a first soft ferromagnetic layer, a second soft ferromagnetic layer, an intermediate layer disposed between the first hard ferromagnetic layer and the first soft ferromagnetic layer, an insulating layer between the first soft ferromagnetic layer and second soft ferromagnetic layer, and a spacer layer disposed between the second soft ferromagnetic layer and the second hard ferromagnetic layer, wherein the second soft ferromagnetic layer increases an on/off ratio of a magnetic field in the first soft ferromagnetic layer, wherein the on/off ratio is approximately 1.6, and wherein the second soft ferromagnetic layer pulls a magnetic field of the apparatus into the first soft ferromagnetic layer.