The basis for work of the majority magnetoresistors serving as the sensors of current is the dependence of resistance on magnetic field, so-called magnetoresistance effect (MRE).

The main objective of the proposed investigations was to enhance the sensitivity of the sensor of current. New design of the sensor of current based on MRE was developed and studied. The sensor was produced in the form of annular magnet with gap from material characterized by high magnetic induction in small magnetic field (ferrites or permalloy). To improve the sensitivity of the sensor, the (La_0.7Sr_0.3)_0.8Мn_1.2О₃ film as the magnetosensitive element was used. This element  possesses both the high metal-insulator transition temperature (above room temperature) and large negative MRE. It was inserted into the gap of magnet. At the current in the conduction line of about 1 A, the magnetic field in the gap of 1 mm reaches the value of about 1 T, and the magnetoresistance effect of several tens of percentage is obtained. The limit of the change of current depends on the size of the gap in the annular magnet and can be changed from tenth parts to a hundred of amperes. At the same time the temperature dependence of magnetic permeability changes insignificantly.

Due to high sensitivity, the large limits of the measured current values, lack of moving electric contacts and high reliability the proposed sensors of current based on MRE can be applied in many electrical arrangements and devices.

This work was in part financed by the Polish Ministry of Education and Science as a Targeted Research Project, over the period 2005–2008 (Project PBZ-KBN-115/T08/01).

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