SU1081576A1 - Method of measuring magnetic field by magnetoresistive pickup - Google Patents

Abstract

METHOD OF MEASURING A MAGNETIC FIELD BY A MAGNETIC RESISTANT SENSOR In which the sensor is fed with a periodic voltage, and the magnetic field is determined by the relative increment of the sensor resistance, characterized in that, in order to increase the sensitivity, the sensor is cooled to a temperature below 10 K, and alternately energizes the sensor for increasing sensitivity, the sensor is cooled to a temperature below 10 K, and alternately energizes the sensor for increasing sensitivity, the sensor is cooled to a temperature below 10 K, and alternately energizes the sensor for increasing sensitivity. with a smaller value, 30–90% less, and with a larger value, 10–50% more than the impurity sample voltage of the sensor material, and the magnitude of the magnetic field is determined by the sum of the ratio th change kn resistance sensor in a magnetic field at a lower and at higher values of voltage powering. x ate to:

Description

The invention relates to magnetic measurements and can be used in low-temperature electrical engineering.

A known method of measuring a magnetic field by a magnetoresistive sensor, in which the sensor is placed in the magnetic field under study, and the field strength is determined by the magnitude of the relative resistance increment of the resistor 13.

The disadvantages of this method are the temperature instability of the zero signal and low sensitivity determined only by an increase in the magnetoresistance of the sensor material in a magnetic field.

The closest in technical essence to the present invention is a method for measuring a magnetic field with two magnetoresistive sensors, in which the sensors supply

periodic opposite polarity voltage of the same amplitude, synchronously with it create a bias field, while receiving periodic alternation of positive and negative increments of resistance of the sensors, the magnitude of which determines the value of the magnetic field C2.

However, this method is folded into implementation, it requires two sensors, a biasing unit, a modulation circuit and an output signal detection, while its sensitivity at temperatures below 10 K is the same as at 300 K and does not exceed the sensitivity of the known method.

The purpose of the invention is to increase the sensitivity of the method of measuring a magnetic field by a magnetoresistive sensor at operating temperatures below 10 K.

The goal is achieved by the method of measuring a magnetic field by a magnetoresistive sensor, in which the sensor is supplied with a periodic voltage, and the magnetic field is determined by the relative increment of the sensor resistance, the sensor is cooled to a temperature below 10 K and alternately powered by a voltage with a lower value by less and with a large value 10-50% more than the voltage of the impurity breakdown of the sensor material, and the magnitude of the magnetic field is determined by the sum of the relative change in resistance tance of the sensor in a magnetic field .If smaller and larger values of voltage powering.

The increase in sensitivity in the proposed method is due to the fact that the magnitude and nature of the change in the resistance of a magnetoresistive sensor at low temperatures in a magnetic field depends on the magnitude of the electric field applied to the sensor, namely in a weak electric field less than the low-temperature impurity sample field, the resistance of the sensor in the magnetic field decreases (the negative magnetoresistive effect), and in a larger field the breakdown increases (the positive magnetoresistive effect).

The boundary of the voltage applied to the voltage sensor by 30% less than the voltage of the impurity breakdown is due to a decrease in the negative magnetoresistance when approaching the breakdown, and by 90% to the noise voltage. The boundary is greater by 10% due to the possibility of breakdown of the magnetic field at lower fields, and 50% overheating of the sensor when more Voltage is applied.

In addition to reducing the temperature instability of the zero signal, which is associated with the possibility of averaging the measured magnetoresistive effect by known devices due to the sensor power supply with a periodic voltage, the proposed method provides additional compensation for temperature instability, also leading to an increase in the threshold sensitivity. Indeed, a temperature increase (decrease) in the resistance of the sensor LR / R g leads to a decrease (increase) in the relative change of its resistance by a magnetic field in the region of a negative magnetoresistive effect.

ufT LEY LNT

   - And increase

“Oh oh

(decrease) in the region of the positive magnetoresistive effect

lk;

4R R,

R,

Ltd

The total change in resistance of the sensor will be equal to

lk

 .R; .

    I

-D- t

Tg

PP I 1, 0 about

whence it is seen that the temperature change in the resistance of the sensor is summed with opposite signs, which leads to a decrease in the temperature instability of the measurements.

Fig. 1 shows the voltage form with which the magnetoresistive sensor is powered; 2 is a calibration graph for a sensor made from gallium p-arsenide.

An example of the practical implementation of the proposed method is the measurement of the magnetic field of a superconducting solenoid at T 4.2 K by a magnetoresistive sensor made of gallium p-arsenide with a carrier concentration of 4.6 10 cm. The field strength of the low-temperature impurity breakdown in such a 9 V sensor cm. The sensor is placed in the working volume of the solenoid and periodically, a voltage is applied, the form of which is shown in Fig. 1, which provides the voltage of the electric field in the sensor 1 V / cm and 10 V / cm. The relative decrease in the resistance of the sensor to the magnetic field is determined at an electric field strength of 1 V / cm and the relative increase is at 10 V / cm. The magnitude of the magnetic field is determined from the calibration curve (Fig. 2) of the amount of the relative change in the resistance of the sensor by the magnetic field in the breakdown field. and post-breakdown electric field. Thus, in a magnetic field with a strength of 3 kOe, the relative decrease in the resistance of the sensor when the electric field is 1 V / cm is 5% and the increase at 10 V / cm is 5%. The sum of the relative change in the resistance of the sensor is 10%, therefore, the absolute sensitivity in this case is two times the sensitivity of methods based on determining the magnetic field by the magnitude of the relative increase in the resistance of the sensor in a magnetic field. Thus, the proposed method provides a measurement of weaker magnetic fields than the known method.

Claims (1)

METHOD FOR MEASURING A MAGNETIC FIELD BY A MAGNETIC RESISTIVE SENSOR, in which the sensor is fed with a periodic voltage, and the magnetic field is determined by the value of the relative increment of the sensor resistance, characterized in that, in order to increase the sensitivity, the sensor is cooled to a temperature below 10 K, and alternately energized with a lower voltage a value of 30-90% less, and with a large value 10-50% more than the voltage of the impurity breakdown of the sensor material, and the magnitude of the magnetic field is determined by the sum of the relative q changes in the resistance of the sensor in a magnetic field with a lower and a higher supply voltage. l Fig.]