B-Scalar Sensor Using CMR Effect in Thin Polycrystalline Manganite Films

We present the design and the main characteristics of the CMR-B-scalar sensor based on polycrystalline La_0.83Sr_0.17MnO₃ films. The sensor active volume is only 400 μm × 50 μm × 0.4 μm, and it is able to measure a magnetic induction of up to 40 T independently on its direction. The investigations of the influence of film preparation conditions on the sensitivity of the device to magnetic field amplitudes, its direction, and ambient temperature variations are presented and discussed. It is demonstrated that, for room temperature conditions, sensors based on films deposited on a lucalox substrate at a 700°C temperature are most suitable. They have a low anisotropy effect (7% at 0.5 T and 3% at higher fields) and significant magnetoresistance values (~30% at 10 T). The dynamics of a CMR response to pulsed magnetic fields is shown, and the operational speed of the sensor is discussed. Moreover, the investigations of electromotive forces induced by a "loop" effect in the bias current cable are presented. A practical solution to counter this effect is offered.