Dresden 2009 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 23: Magnetic Thin Films II

MA 23.10: Vortrag

Mittwoch, 25. März 2009, 17:00–17:15, HSZ 04

Non-contact Temperature Sensor Based on Inverse Magnetostriction — •Claas Thede, Steffen Chemnitz, and Eckhard Quandt — Christian-Albrechts-Universität zu Kiel

Sensors based on magnetic effects can be used for non-contact measurement. We present such a sensor capable of determining the thickness and also the temperature of magnetostrictive thin films.

These films can be prepared as multilayers of magnetostrictive and non-magnetostrictive material or by embedding a magnetostrictive phase into a bulk material. In both options the amount of magnetic material is related directly to the overall film thickness. Temperature measurement is achieved due to the magnetostrictive properties of the films and the difference in strain modulus between the films and their supporting material. Thus temperature induces mechanical stress, which is linked to the permeability.

The magnetic thin films act as a magnetic core for a measurement coil, which is part of an LC-oscillator driven at its resonance frequency. The presence of magnetic material affects the coils inductance and therefore shifts the resonance frequency. This generates a phase discrepancy between the oscillator and its driving circuit, as the temperature-induced change of the materials permeability does, too. By applying an additional external magnetic field the signal can be separated from the background while the monitoring of the spectral response to the saturation allows to distinguish the two effects.

Funding by the DFG via the priority program 1299 "HAUT" is gratefully acknowledged.