Design optimization for a SmCo-biased colossal magnetoresistive thin film device

A device structure composed primarily of a film made from colossal magnetoresistive (CMR) material and a permanent magnet (PM) film used for biasing the CMR film is proposed as a sensor for magnetic objects. The PM film provides a magnetic field through the CMR film, which is substantially decreased when a magnetic object approaches the device, as part of the magnetic flux is now diverted through the object. To test the feasibility of this concept, we performed simulations of the magnetic field distribution with a three-dimensional finite boundary program. Our vertical model structure consists of a strip of CMR material covered by a PM strip with magnetic in-plane texture and magnetized along its width. The maximum possible biasing field through the CMR material is mainly controlled by the thickness to width ratio of the PM material and cannot be improved by the use of a soft magnetic cladding. The same effect is observed on the flux reduction by approaching a magnetic object. Preliminary results on an experimental realization of the device are given. (C) 2000 American Institute of Physics. [S0021-8979(00)61808-X].