SU1282029A1 - Magnetooptical hysteresis curve recorder - Google Patents

Abstract

The invention relates to the field of magnetic measuring equipment, in particular to magneto-optical hysterograps for recording a quasistatic magnetic hysteresis loop. based on the effects of Kerr and Farad. The aim of the invention is to improve the measurement accuracy. To achieve this goal, a lens 9, a rotating analyzer 10, a second photodetector 18, and a second radiation source 17 are additionally introduced into the device. The drawing also shows the magnetizing system 1, the generator 2 of the magnetizing current, the transducer 3 of the magnetic field into an electric signal, sample 4, the polarizer 5, the first radiation source 6, the compensator 7, the two-beam analyzer 8, the first photodetector 11, the narrowband amplifier 12, synchronous detector 13, amplifier 14, direct current, shunt element 15, recorder 16. 1 Il. i Ш С

Description

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The invention relates to a magnetic and measuring technique, in particular, to magneto-optical hysterografes for recording a quasistatic magnetic hysteresis loop based on the effects of Kerr and Farad.

The purpose of the invention is to increase the measurement accuracy.

The drawing shows a functional block diagram of an optical hysterograph.

The magneto-optical hysterographer contains a magnetizing system 1 with a generator 2 of a magnetizing current by a converter 3 of a magnetic field into an electric signal and a sample 4 optically coupled through a polarizer 5 to a first source 6 of radiation, and through a compensator 7j a two-beam analyzer 8, lens 9 and a rotating analyzer 10 — with the first photodetector 11. In series with the latter, a narrowband amplifier 12, a synchronous detector 13, an amplifier 14 of direct current, a winding of the compensator 7, and a connecting element 15 are included. the transducer stroke 3 is connected to the X-input of the regigl-rator 16, the output of the shunting element 15 is connected to the V-input. The reference input of the synchronous detector 13 is connected to the output of the second photodetector tSj optically coupled through the shutter of the rotator 10 to the second radiation source 17.

The device works as follows.

A generator and a magnetized generator produces a slowly (with frequency i) 40 sweeping current, which is transformed by a magnetizing system and a magnetic field of magnitude 1J, re magnetizing the sample 4, the flux of the first source 6, linearly 45 polarized by polarizer 5, falls on sample 4, the azimuth of polarization of the flow reflected from sample 4 is changed by an angle proportional to the magnetization of sample 4. Passed 50 through the compensator 7, which changes the polarization azimuth by an angle proportional to the current in the winding of the compensator 1 the radiation flux is divided into two 55 orthogonally polarized components by a two-indicator detector; the Azimuth of the analyzer 8 is an angle of 45 with the polarization plane of the flux incident on the sample 5;

therefore, the intensities of the fluxes coming out of the two-beam analyzer 8 are different by an amount proportional to the sum of the rotation angles of the polarization plane in sample 4 and the compensator 7. Lens 9 focuses both streams on the first photodetector 11, and, having passed through the rotating analyzer 10, the streams are modulated by sinusoidal law with a frequency equal to twice the frequency of rotation of the analyzer 10. Since the plane of polarization of the flows are at an angle of 90 ° to each other, their modulation is in antiphase with the total flow, pa The sensor to the photoreceiver 11 is converted into an electrical signal, the harmonic of which, having a frequency equal to the modulation frequency, is amplified by a narrowband amplifier 12, allocated to the signal of the forgated photoreceiver 18 by the synchronous reference detector 13, the voltage is converted by the amplifier 14 to a current, defines em. azkG Turnout of the compensator 7. In the negative feedback ring thus formed, the angle of rotation of the polarization plane in sample 4 is compensated by rotating the polarization plane in the compensator 7 in the opposite direction. The voltage j is proportional to the current, and the compensator 7 winding is removed from A shunt 15 is applied to the Y input of a two-coordinate recorder 1 &, and the X input of which is supplied with a voltage from a transformer 3 of the magnetic field to an electrical signal.

. . Such o6pa3OMs on the two-coordinate registrater 16 register a hysteresis loop of the illuminated part of the sample under study 4.

The output streams (T -,) of the analyzer 8 are described by the following expression.

1L

--f g 81p () + k,

where CR is the radiation flux incident

on the sample;

g is the reflection coefficient of the sample;

F t H TG / 4 angles of rotation of the i-plane of polarization in the sample, the compass torus, and the azimuthal modulator;

K is the depolarization coefficient of radiation from the sample surface. After - transform receive

9 .- T r (1 + 2K) + sin2 (y + v (.).

ii

Modulated by intensity in rotating with frequency and analyzer 10, the streams are described by the following expressions:

F,

fgM (I-2K) +2 () (H-sin2SJt);

Ф- | ф г.С (Ц-2К) +2 (Ч + Ч) (1-sin2Qt).

The total flow received by the photodetector is

, -F | f gCh (1 + 2K) +2 (H + H) 181p2as.

If we consider J, that the first harmonic of the flow with the frequency cJ is equal to

, f cf j. l (4) + v)

and gradually, the component is

% | F CHI-2K)

then, for K? 1 and (), the normalized signal-to-noise ratio is described by the following expression:

Claims (1)

Invention Formula five A magneto-optical hysterographer containing a magnetizing system 5- with a magnetizing current generator with a magnetic field transformer into an electrical signal and a sample optically coupled through a polarizer with the first radiation source, and a recorder connected in series with a photodetector, narrowband amplifier, synchronous a detector, a DC amplifier, a current, a compensator winding and a shunt element, the X-input | of the recorder connected to the output of the preamp the intensity of the magnetic field in the electrical signal, and the Y input 0 with the output of a shunt element, characterized in that, in order to improve accuracy, a second radiation source, a second photodetector, a lens and a rotating analyzer are inserted in it, the analyzer being dual-beam, and each of its outputs is optically coupled through a sequentially mounted lens and rotating analyzer to a first photo receiver, the reference input of a synchronous detector is connected to the output of a second photo receiver optically coupled through a shutter raschayuschegos analyzer with a second source ie- heaving. five