RU2828619C1 - Magnetometer on yig film with oscillating magnetization - Google Patents

Abstract

FIELD: measuring.

SUBSTANCE: invention relates to measurement equipment and is intended for measurement of permanent or alternating magnetic fields. Magnetometer comprises a YIG film with light plane anisotropy, a band-pass filter, a reference and variable signal multiplier and an integrator for generating a feedback signal and an output signal of the magnetometer, an additional reference oscillating circuit forming a balance circuit with the main oscillating circuit.

EFFECT: high sensitivity of the magnetometer.

1 cl, 1 dwg

Description

A magnetometer on a YIG film with oscillating magnetization (hereinafter referred to as a magnetometer) is related to measuring equipment and is intended for measuring constant or variable magnetic fields. The magnetometer is intended for measuring the inductance of relatively weak fields (up to tens of pT), localized in a small area (from 5 mm ³ ).

Among the currently existing inventions, the following analogs of a magnetometer can be distinguished.

Magnetometer (patent GB 1510732, 17.05.1978), containing an inductance coil with an alternating signal, wound on a film saturated with a magnetic field. The field is estimated by the zero method by balancing the measured field due to the feedback system.

A thin-film magnetometer using an orthogonal flux isolator (US Patent 4007417, 08.02.1977) containing an inductor with a sinusoidal signal and a feedback system.

A method for measuring magnetic fields and a magnetometer for implementing the method (patent GB 1402798, 13.08.1975), containing a coil wound around a single-domain film, as part of an oscillatory circuit, and also having a balancing feedback coil.

The closest analogue (prototype) in terms of the set of essential features is a magnetometer (patent DE 1909435, 20.08.1970), containing a parallel oscillatory circuit with a trimmer capacitor; the resonant frequency of the circuit is detuned from the frequency of the quartz generator 10 MHz. There is a compensating feedback coil wound on a magnetosensitive element.

A significant difference between the proposed magnetometer and the prototype is the use of a thin YIG film with a wide frequency range (hundreds of MHz) and extremely low electromagnetic losses (up to 20 dB/μs) as a sensitive element of the magnetometer. This component of the magnetometer has an easy-plane anisotropy, so the orientation of the film relative to the coils of the oscillatory circuits and feedback does not matter. Another difference is the presence of an additional reference oscillatory circuit, to which an inverted signal from the quartz generator is fed. Parallel connection of two circuits forms a balanced circuit, due to which the noise level from the reference generator is reduced. A bandpass filter for the frequency of the quartz resonator is added to the device circuit to prevent non-periodic noise from the sensitive element of the circuit. A multiplier of the reference and variable signals, as well as a linear integrator are used to generate a feedback signal and an output signal of the magnetometer.

The features that distinguish the claimed technical solution from the prototype have not been identified in other technical solutions.

The technical result is an increase in the sensitivity of the magnetometer.

The technical result is achieved in that the magnetometer contains a YIG film with an easy plane anisotropy, a bandpass filter, a multiplier of the reference and variable signals and an integrator for generating a feedback signal and an output signal of the magnetometer, an additional reference oscillatory circuit that forms a balanced circuit with the main oscillatory circuit.

Fig. 1 shows the general diagram of the magnetometer.

The magnetometer uses a YIG film 1 with easy-plane anisotropy as a sensitive element. The YIG film 1 acts as a coil core, which is part of the main oscillatory circuit 2, tuned using a tuning capacitor from the frequency of the 10 MHz master quartz generator 3. To reduce the generator's own noise, an additional reference oscillatory circuit 4 is included, which is a component of the balanced circuit with the main oscillatory circuit 2. In this case, the balanced circuit is called the connection of two oscillatory circuits at one point - the main oscillatory circuit 2 and the additional reference oscillatory circuit 4. The inductance value of the additional reference oscillatory circuit 4 corresponds to the inductance of the main oscillatory circuit 2 in a single-domain operating state in the absence of measurable external fields. Maintaining the YIG film 1 in a single-domain state and stabilizing the magnetization vector is ensured by the feedback coil 5, wound around the YIG film 1 perpendicular to the coil of the main oscillatory circuit 2. The current of the feedback coil 5 is formed by the amplifier 6 of the feedback coil of the magnetometer output signal. The signals formed by the quartz generator 3 and fed to circuits 2 and 4 are corrected in amplitude by amplifiers 7 and 8. In this case, the amplifier 8 has an inverted signal at the output. Then the signal from the balanced circuit of circuits 2 and 4 is processed by bandpass filter 9 to eliminate noise components produced by YIG film 1. An important element of the circuit is the multiplier of the reference and variable signals 10, which receives the filtered signal from circuits 2 and 4 and the reference signal from the quartz generator 3, shifted by 90° in phase 11, amplified by amplifier 12. Depending on the magnitude of the external measured field, the magnetization vector of YIG film 1 can change its magnitude and direction, thus changing the inductance of the feedback coil 5 in the main oscillatory circuit 2 and, accordingly, shifting the current relative to the voltage. For this reason, the signal at the output of the multiplier of the reference and variable signals 10 changes depending on the measured magnetic field. For the linearization of the variable signal from the multiplier of the reference and variable signals 10 and its subsequent use in the feedback branch as a compensating signal, the integrator 13 is used. The signal from the integrator 13, fed to the feedback coil 5, maintains the YIG film 1 in a single-domain state, and is also the output signal of the magnetometer.

One of the options for implementing the magnetometer may be its use as part of a measuring complex for characterizing the distribution of ferromagnetic materials in various objects. For example, in the promising field of medicine, theranostics of oncological diseases, the invention can act as a detector of biocompatible ferromagnetic nanoparticles capable of attaching to cancer cells. After exposure to an external pulsed field, the particles become point sources of a magnetic field, the magnitude of which must be detected by the detector. An array of detectors allows obtaining a set of data by which it is possible to determine the location of the particles and, thus, solve the inverse tomography problem.

The magnetometer device can be implemented on a printed circuit board using modern surface-mount components. The material for winding around the film can be PELSHO cable (enamelled wire with oil-based insulation and silk winding). The combined type of insulation increases the mechanical, electrical and thermal strength of the winding products. Using a cable with a silk winding allows you to reduce the parasitic capacitance of the oscillatory circuit, providing a higher quality factor compared to a conventional cable. To reduce parasitic noise from YIG interference, the film should be shielded with copper foil connected to the ground circuit of the electrical circuit.

The described magnetometer is capable of recording fields from ferromagnetic nanoparticles with induction of tens of pT in a non-magnetic chamber. The analog signal at the device output can be evaluated using an oscilloscope or digitized and examined on a computer.

The expected characteristics of the magnetometer on the YIG film with oscillating magnetization can be characterized as follows. The upper limit of the frequency range of the magnetometer is up to 100 kHz, and the lower limit of the force values of the measured magnetic fields is tens of pT.

Thus, the proposed magnetometer ensures the achievement of the required technical result, which consists in increasing the sensitivity of the magnetometer.

Claims (1)

A magnetometer on a YIG film with oscillating magnetization, comprising a main oscillatory circuit with a tuning capacitor and detuned from the frequency of a quartz generator, including a feedback system in the form of a compensating coil, characterized in that the magnetometer contains a YIG film with anisotropy of the easy plane type, a feedback coil wound around the YIG film perpendicular to the coil of the main oscillatory circuit, an additional reference oscillatory circuit that forms a balanced circuit with the main oscillatory circuit, a bandpass filter, amplifiers that provide correction of the signal by amplitude, generated by the quartz generator and fed to the main oscillatory circuit, and an additional reference oscillatory circuit, wherein the electrical circuit of the magnetometer uses a filtered signal obtained from the main oscillatory circuit and the additional reference oscillatory circuit and shifted by 90° in phase, transmitted to the multiplier of the reference and variable signals, in addition, the electrical circuit of the magnetometer contains an integrator that linearizes the alternating signal from the multiplier of the reference and variable signals and its subsequent transmission to the feedback coil to maintain the YIG film in a single-domain state.