A new class of LC-resonator for micro-magnetic sensor application

A new class of LC-resonators for micro-magnetic sensor device was invented and fabricated by means of micro-electromechanical system (MEMS) technique. The micro-LC-resonator consists of a solenoidal micro-inductor with a bundle of soft magnetic micro-wire cores and a capacitor connected in parallel to the micro-inductor. The core magnetic material is a tiny glass-coated Co83.2B3.3Si5.9Mn7.6 micro-wire fabricated by a glass-coated melt spinning technique. The core materials were annealed at various temperatures 150, 200, 250, and 300 1C for 1 h in a vacuum to improve soft magnetic properties. The solenoidal micro-inductors fabricated by MEMS technique were 500–1000 mm in length with 10–20 turns. The changes of inductance as a function of external magnetic field in micro-inductors with properly annealed micro-wire cores were varied as much as 370%, since the permeability of ultrasoft magnetic micro-wire changes rapidly as a function of external magnetic field. The inductance ratio as well as magnetoimpedance ratio (MIR) in an LC-resonator was varied drastically as a function of external magnetic field. The MIR curves can be tuned very precisely to obtain maximum sensitivity. r 2006 Elsevier B.V. All rights reserved. PACS: 75.50.kj; 76.90.+d