Magnetic sensor and magnetic field sensing method of using same based on impedance changes of a high frequency supplied conductor

A magnetic field sensing apparatus, comprising:

• a magnetic sensor comprising a conductor and at least one magnetic material provided so as to enclose a peripheW of said conductor, wherein a gap is provided in a portion of a magnetic circuit formed by said magnetic material, said gap facing an external magnetic field which is to be sensed, and wherein said conductor comprises two ends, said magnetic material being formed with a multi-layered structure in which magnetic layers and non-magnetic insulator layers are alternatively layered, a thickness of each magnetic layer being thinner than a skin depth, and each non-magnetic insulator layer having a thickness capable of at least maintaining electrical insulation between the magnetic layers;
• a high frequency generator for supplying, through two lead wires, a high frequency current to said conductor, the frequency of the high frequency current being approximately equal to a magnetic resonance frequency of the magnetic material supplied a to the conductor;
• and
• a detector for detecting, through two other lead wires, changes in voltage amplitude obtained at both ends of said conductor by converting changes in impedance of said conductor due to the magnetic material, in accordance with the external magnetic field, into voltage changes by means of a four-terminal method.