RU1781650C - Device for study of magnetic properties of matters - Google Patents

Description

1

(21) 4852746/21

(22) 07.19.90

(46) 12/15/92 Bull. №46

(71) Leningrad Institute of Nuclear Physics named after B.P. Konstantinova

(72) I.I. Larinov, V.A. Ryzhov and VN Fomichev

(56) 1. Anisimov GK et al. On the Use of Nonlinear Effects in Paramagnets in Parallel Magnetic Fields for the Study of Paramagnetic Substances, ZhTF, 1982, v. 52. No. 1, pp. 74-81.

(54) DEVICE FOR RESEARCH OF MAGNETIC PROPERTIES OF SUBSTANCES

(57) The invention in the device ampoule with the analyte is placed

in the gap of the electromagnet together with a high-frequency inductor The electric circuit of the device includes a serial circuit, a high-frequency generator, a communication element, a tuning capacitor, a high-pass filter, a receiver, a digital recording system, as well as a parallel circuit. In this case, the inductor is made of air and equipped with heat shields, and the surfaces of the coils: capacitors, shields and conductors are coated with a conductive coating with a content of ferromagnetic impurities and a thickness satisfying given conditions m. 2 s ss, 4 silt

T ± S

ё

The invention relates to techniques for studying the magnetic properties of substances based on spin effects, to the field of scientific instrumentation and can be used to study paramagnetic, ferromagnetic or atiferromagnetic substances in chemistry, solid state physics, high-temperature superconductors, semiconductor:

NIKOV AND ETC.

It is known that in constant and alternating parallel magnetic fields, the magnetization of the sample under study nonlinearly depends on their magnitude due to the existence of nonlinear effects. Nonlinear effects in parallel magnetic fields may be due to:

the influence of the alternating field on relaxation processes (in this case, it is possible to obtain information on the mechanisms and effective V relaxation),

resonant transitions in parallel fields, which makes it possible to obtain spectroscopic information;

the influence of the alternating field on the behavior of the spin system under conditions of adiabatic (in the thermodynamic sense) action in magnetically concentrated paramagnets (in this case, information can be obtained on the features of the collective behavior of spins;

nonlinearity of the magnetization curve, which is the case for ferromagnets and antiferromagnets or for paramagnets in the region of very strong magnetic fields, it is possible to obtain information about the shape of the magnetization curve, relaxation times of the macroscopic moment, etc.

The magnetic properties of substances, vividly dynamic, were previously studied as in parallel magnetic fields,

VI

00 SE

word about

and in the fields x directed at an angle. In the experiment, a longitudinal linear response was recorded, i.e. a signal due to the magnetization of the sample in the direction of a constant magnetic field at the excitation frequency.

The development of this approach has become the method of electron paramagnetic resonance (EPR), the most sensitive and most widely used method of studying magnetic properties, in which the orientation of the fields is perpendicular and the response is recorded at the excitation frequency. Registration at the excitation frequency has a serious methodological disadvantage: a weak response signal is detected against the background of a large field of excitation. In this case, the signal-to-noise ratio is determined not by the noise of the receiver, but by the noise of the drive device. This disadvantage can be avoided under conditions of a nonlinear response when a signal is recorded at a frequency of any harmonic of the excitation frequency, even when exposed to a strong alternating field. Higher harmonics from the generator side and the first harmonic at the receiver input are suppressed by frequency selection methods, and the signal is measured against the background of thermal noise receiver

In the case of short relaxation times, when the resonance transitions recorded in the EPR are greatly broadened and therefore unobservable, the nonlinearity in parallel fields can remain large and the sensitivity of this method in this case exceeds the sensitivity of the EPR method. Another advantage of the method is the fundamental possibility of obtaining information on the times and mechanisms of spin-lattice relaxation, which is difficult to access by the EPR method.

A device for studying the magnetic properties of substances based on non-linear response is known. The device contains an electromagnet, in the MCL gap of which is placed a two-mode pass-through resonator of the TEU2 type connected through a low-pass filter with a microwave generator at a frequency of 2, 7 GHz and through a band-pass filter with a superheterodyne receiver at a frequency of 5, 4 GHz. The signal due to resonant nonlinear effects is recorded only when the alternating microwave magnetic field is oriented at an angle to a constant and is not observed when they are parallel oriented, which indicates a low sensitivity of the device

Closest to the proposed device in technical essence is a device for studying the magnetic properties of substances, designed to study nonlinear effects in substances in parallel magnetic fields, contains a DC electromagnet with magnetic field sweep coils, in the inter-pole gap of which there is a high-frequency (HF) an inductor included in the two-frequency resonant circuit into which the ampoule with the test substance is inserted. Two-frequency resonant circuit, in addition,

contains a resonance adjustment capacitor connected in parallel with the RF coil at the excitation frequency o) and a series circuit consisting of an inductor with a coupling loop and a capacitor

tuning resonance at a frequency of 2 a (31.4 MHz). as well as a communication element.

The device also includes a high-frequency generator which, through a low-pass filter, is coupled to a two-frequency resonant circuit using a coupling element. (The coupling element is a coil inductively coupled to an RF coil of a dual frequency resonant circuit). The low-pass filter suppresses the harmonics of the excitation frequency from the generator by more than 90 dB. In addition, the device comprises a receiver, which is inductively connected through a high-pass filter to the inductance coil of a series circuit using a coil

communication. A high-pass filter provides suppression at a driving frequency of at least 80 dB.

The device also comprises a digital signal registration and accumulation system (DSCNS), the input of which is connected to the output of the receiver. CSRNS through amplifier

power is connected to the sweep coils of a constant magnetic field. The device is equipped with a thermal stabilization system using evaporated nitrogen as a refrigerant, which provides cooling

and stabilization of the temperature of all inductors included in the two frequency resonant circuit, and thereby stable tuning of this circuit to frequencies o) and 2 °.

The disadvantage of this prototype device is its low sensitivity, which is due to the large spurious signal arising due to nonlinear effects in the materials used in

elements of a 2-frequency resonant circuit, 90 dB higher than the thermal noise level of the receiver.

In order to isolate the signal from the test sample (useful signal) at the second harmonic, the separately recorded spurious signal must be subtracted from its sum with the useful one. When the desired signal is commensurate with the noise level, an accumulation of the order of measurement 10 is necessary to obtain a signal to noise ratio of 40 dB. In this case, the presence of a spurious signal makes it necessary to have a dynamic range of the recording path of 130 dB (40 dB + 90 dB) and, accordingly, a 22-bit amplitude-to-digital conversion. Such ADCs have long conversion times and the accumulation of 10 -10 measurements will require tens of hours. Ensuring the amplitude-phase stability of a device at a level is an extremely difficult task. By subtraction, it is possible to isolate the useful signal from the sum with the spurious signal if it is less than 30 dB less than the spurious signal. Thus, the presence of a large spurious signal imposes a significant limitation on the sensitivity of the device.

In addition, together with the formation of a spurious signal, the noise spectrum of the excitation generator is converted to a frequency of 2 W, and the level of this noise is significantly higher than the noise level of the receiver. Subtraction of the spurious signal, even if the technical parameters necessary for this are provided, only increases the noise background, since the noise is not correlated, and when subtracting, as in addition, it increases / N, where N is the number of subtractions, i.e. Subtraction cannot fundamentally eliminate all the troubles associated with the presence of a spurious signal.

The aim of the invention is to increase the sensitivity of the device by eliminating the spurious signal. Achieving this goal allows one to work with paramagnets in both the liquid and solid phases, previously inaccessible for studying their dynamic properties by radio frequency methods. Examples are ferric iron solutions 1 or compounds of the LaaCuO type, which are of great interest in connection with the appearance of high-temperature superconductors based on them. An EPR signal is absent in these compounds, while in the proposed device the signal is observed even at room and higher temperatures

A device for studying the magnetic properties of substances containing a direct current electromagnet with magnetic field sweep coils whose pole gap contains an ampoule for the test substance and a high-frequency inductor connected in parallel to a serial circuit in the form of an inductance coil with a coupling loop and a second harmonic frequency tuning capacitor , a high-frequency generator, the output of which is connected to the input of a low-pass filter, the output of which is connected to the input of the element zi, the first harmonic frequency tuning capacitor, the first output of which is connected to the first output of the high-frequency inductor and a common bus, a high-pass filter, a receiver, a digital signal recording and accumulation system, and a power amplifier, the output of which is connected to the magnetic field sweep coils of the electromagnet direct current, and the conclusions of the loop of the coil of the inductance of the serial circuit are connected to the input of the high-pass filter and a common bus, and high-frequency the coil and the inductance coil with a serial communication loop are made with thermal stabilization systems, equipped with a parallel circuit in the form of an air inductance with a thermal stabilization system and a capacitor connected between the second terminals of the high-frequency inductor and the capacitor of tuning to the frequency of the first harmonic, the terminals of which are also connected to the outputs e element of communication. In addition, unlike the prototype, the high-frequency coil of the IHCT inductance, the inductance coil with a loop of communication in series and air circuits, and thermostabilization systems are made with heat shields, and the high-frequency inductor, inductors and capacitors in series and parallel loops, zi, capacitor for tuning to the frequency of the first harmonic, connecting conductors between the above elements and the inner surfaces of the heat shields of thermostat systems The processes are carried out with a conductive coating, the content of impurities of ferromagnetic metals and the thickness of which satisfy the conditions:

Sp Ј 9.6 10 4HG2 (T A f F) 1/2, (l-a- / l-w) 1/2 where Sp. - the content of impurities of ferromagnetic metals,%,

Hi - the amplitude of the high-frequency magnetic field on the surface of the corresponding element, E,

T is the temperature of the input active element of the receiver, K;

F is the noise factor of the first active element of the receiver, dB;

L f is the receiver bandwidth, Hz;

L is the thickness of the conductive coating, M;

, -f.io ca - magnetic permeability of the conductive coating, H / M;

with 2 f - cyclic frequency of the first harmonic, rad / sec.

In addition, unlike the prototype, the communication element is made in the form of a capacitive divider, the middle point and extreme points of which are connected to the input and outputs of the communication element, respectively.

In this case, the ampoule for the test substance is made of a dielectric material with a dielectric loss tangent and the content of impurities of ferromagnetic metals satisfying the conditions:

tg Y, SpR $ 9 6 KG (T L f to "F) 1/2.

Firstly, the parallel resonant circuit introduced into the device substantially reduces the contribution to the total spurious signal in the receiving coil of the serial circuit from the spurious signal arising in the tuning capacitor at frequency o and in the coupling element (capacitive divider). Secondly, this circuit makes it possible to increase the fraction of the useful signal arising from the sample in the high-frequency coil in the same coil, since the parallel circuit prevents the serial circuit from being shunted at a frequency of 2 a) by a capacitive divider and a resonance tuning capacitor at a frequency (o.

The thermal stabilization systems of the inductors are made with heat-insulating shields, in which a high-frequency coil, an inductor with a coupling loop of a serial circuit and a parallel circuit inductor are placed. This makes it possible to stabilize their temperature and achieve stable tuning of the two-frequency resonant circuit with the required power level of the BC generator.

In the invention, the high-frequency inductor, inductors and capacitors of series and parallel circuits, the coupling element, all the connecting wires, and also the inner surfaces of the heat-insulating shields are made with a conductive coating, the impurities of ferromagnetic metals in which and its thickness satisfy the above relations. The coating thickness is selected at least 3 d, where (5

nineteen

2 / (loc) - the thickness of the skin layer at a frequency w in the coating material. With such a coating thickness, a high-frequency magnetic field arising on the outer side of the coating when frequency O) flows through the coating with RF frequencies. weakens on the surface of the original

M5 .z

material under coating in e

 e times.

This leads to a weakening by a factor of e of the spurious signal from ferromagnetic contaminants in the starting material, because its value is proportional to the square of the RF magnetic field strength in place

location of the impurity. Since the signal is recorded at the second harmonic of 2 m (for it, the skin layer is d 2 2 / (l a / u% 2 m), 2 times less than for the fundamental frequency (l)), its value is

the outer side of the coating will be further weakened by the coating exp (b / d) (2) 1/2 times. The resulting attenuation of the spurious signal from ferromagnetic impurities in the source material

e1 order (W 3 104 times, i.e. 90 dB

All inductors are airborne to allow a clean conductive layer to be applied to these coils after selecting their inductance and putting them in place, i.e. assembled. This eliminates the possibility of contamination of the surfaces of the coils during assembly after applying a clean coating. In addition, if all inductors

made by air, in the RF magnetic field created by these coils, there are no other materials (except the material of the coils) with possible ferromagnetic contamination.

The implementation of the coupling element of the RF generator with a two-frequency resonant circuit in the form of a capacitive divider (capacitive coupling, but not inductive, as in the prototype) allows, firstly, to remove excess elements (coupling coil) from the high-frequency coil with the sample and thereby reducing the number of probable spurious signal sources. Secondly, it allows you to adjust this connection during operation, which

it was impossible for inductive coupling due to structural considerations. In the prototype, the coupling coil covered the high-frequency coil with the sample and to change the coupling it was necessary to change the number of turns in the coupling coil, which is impossible without disassembly. Thirdly, the central core of the cable connecting the RF generator with a two-frequency resonant circuit in the case of capacitive coupling is galvanically isolated from it, which avoids the flow of currents of 50 Hz and other low-frequency currents arising in it due to interference from power chains.

The ampoule for the sample is made of a material, the content of impurities of ferromagnetic metals in which satisfies the above ratio, and the tangent of the dielectric loss angle is not more. The first condition avoids the spurious signal from the ampoule material, which exceeds the input noise of the receiver in amplitude. The second condition is necessary on the basis of the requirement that the ampoule material has a weak effect on the quality factor of the two-frequency resonant circuit (polystyrene, fluoroplastic, optical quartz)

Experimental studies (the results are given in more detail below) showed that, under these conditions, the spurious signal from impurities is lower than the thermal noise at the receiver input.

Comparative analysis with the prototype shows that the proposed device differs from it by the introduction of a new node - a parallel circuit and the special implementation of individual nodes and elements.

In FIG. 1 shows a block diagram of a device; in FIG. 2 is a block diagram and functional communications in a digital signal acquisition and accumulation system; in FIG. 3 is a graph of the variation of the parasitic signal with respect to the nitroxyl radical useful in aqueous solutions of various concentrations, as well as with respect to noise, for the prototype and the proposed device (all curves are experimental): FIG. Figure 4 is a graph of the variation of the spurious signal to noise ratio with a change in the concentration of impurities of ferromagnetic metals.

Example. According to FIG. 1, the device comprises a direct current electromagnet 1 with sweep coils of a constant magnetic field 2. A high frequency inductor 3 is located in the interpolar gap of the electromagnet, the axis of which is oriented parallel to the constant magnetic field created by the electromagnet. A high-frequency coil 3 is placed in a heat-insulating screen 4, an ampoule 5 with a test sample is located inside it. The first output of the coil 3 and the conductive layer on the inner surface of the insulating screen 4 are connected to a common bus at point 6. In parallel

A high-frequency coil 3 is connected through a coaxial wire 7 to a serial circuit consisting of an inductor 8 with a coupling loop in the heat-insulating screen 9 and a resonance tuning capacitor at a frequency of 2ш - 10. Parallel to the serial circuit through a parallel resonant circuit tuned to the frequency 2m and containing an inductor 11 in the heat-insulating screen 12 and a capacitor 13, capacitors 14, 15, 16 are included. A parallel circuit through a coaxial wire 7 is connected between the second terminals of the high-frequency cable carcass 3 and capacitor 16, which serves to adjust the resonance at the excitation frequency a. Capacitors 14 and 15 form a capacitive divider, which is a communication element of the RF generator 17

with a two-frequency resonant circuit. The RF generator 17 is connected through a low-pass filter 18 to the midpoint of the coupling element, thereby matching the output impedance of the two-frequency resonant circuit at the excitation frequency w. The input of the receiver 19 through the high-pass filter 20 and the coupling loop 21 are inductively coupled to the coil 8 of the series circuit. To the output of the receiver 19

connected to a digital signal recording and storage system (DSCNS) 22, which, through a power amplifier 23, controls the current in the scan coils 2 of a constant magnetic field. The thermal stabilization system 24 provides cooling of the inductors 3, 8, 11. placed in the heat-insulating screens 4, 9 and 12, respectively. The thermal stabilization system 25, if necessary, provides for the installation and stabilization of the temperature of sample 5. Evaporated nitrogen is used as the refrigerant in both thermal stabilization systems.

The device operates as follows.

Inside the high-frequency coil 3 is placed an ampoule 5 with the analyte and the coil in a heat-insulating screen

4 together with the scanning coils of the magnetic field 2 is placed in the gap of the electromagnet 1. The electromagnet is turned on. The gas flow is switched on through the heat-insulating screens 4, 9, 12 for coils 3, 8, 11 in order to cool and stabilize their temperature. The high-frequency generator 17 is turned on, and electromagnetic oscillations of frequency w are excited in the two-frequency resonant circuit, as a result of which the sample under investigation is affected

an alternating magnetic field of this frequency parallel to a constant. The tuning of the two-frequency resonant circuit is checked and, if necessary, it is tuned to the frequencies w and 2 with the help of capacitors 10 and 16. The digital system 22 for switching the signal 22 and the power amplifier 23, which controls the current in the DC magnetic coils, are turned on. field, and the necessary range for the observation of the signal from the test sample is set and the sweep frequency of the constant magnetic field. Due to the existence of nonlinear effects in parallel magnetic fields, the response to an external action for the test sample is nonlinear, i.e. its magnetization contains higher harmonics of the excitation frequency u), the amplitude and phase of which depend on the amplitude of the constant magnetic field. Therefore, in the high-frequency coil 3, an EMF of frequency 2sh appears, modulated by the scanning frequency of a constant magnetic field, which excites oscillations at a frequency of 2 m in a two-frequency resonant circuit. As a result, a current at a frequency of 2sh appears in the coil 8 of the serial circuit, which induces an emf through a coupling loop 21 at a frequency of 2 sh at the input of the receiver 19. In this case, the emf at a frequency a) is suppressed by the high-pass filter 20 and does not reach the input receiver. From the output of the receiver, the signal enters the input TsSRNS 22.

Since the DSCRN, by means of a power amplifier 23 and coils 2, periodically sweeps the magnetic field (triangular shape), the signal is a batch process. The DSCNS makes 1024 samples of the signal at the half-cycle of the magnetic field sweep and writes them to its autonomous memory, where each cell corresponds to a certain value of the magnetic field. In the next sweep period, the samples are added to the values already stored in the memory. For N passes of the magnetic field, N sweep periods), since the signal is correlated with the sweep of the field, but there is no noise, the signal amplitude grows N, the noise amplitude (M), and the signal-to-noise ratio (1H), i.e. signal accumulation occurs. The amplitude of the quadrature phase components of the second magnetization harmonic is recorded as a function of the amplitude of the constant magnetic field. The computer communication channel, if necessary, provides the possibility of transferring an array of experimental data from the autonomous memory of the DSSRNS to the computer memory and their mathematical processing.

A specific implementation of the main components of the device is given below.

Receiver 19 includes barrage

a filter 20 for suppressing the frequency voltage a) at the receiver input by 110 dB. a resonant amplifier, which has a 50-ohm input resistance and a voltage gain of 80 dB, a reference voltage shaper 2a with a phase shifter, two quadrature synchronous detectors, and two low-frequency amplifiers (VLF) connected after them with an input resistance of 10 MΩ, a coefficient voltage gains of 0-60 dB and with passband adjustable by active filters, as well as a signal switch. The latter provides

0 alternately turning on the signals from the outputs of the low-frequency amplifiers to the input TsSRNS. A high-power RF generator 17 with an output oscillatory power of 100 W and an output impedance of 75 Ohms is

5 is a master oscillator and three stages of frequency doubling, the last stage being made in a symmetrical manner, which ensures suppression of even harmonics at the output by 60 dB. Additional suppression by 90 dB is achieved using a Chebyshev low-pass filter. For thermal stabilization, the UTS 221 EPR system with a temperature controller 650R manufactured by the Polish company Ragiopan was used.

5 The digital registration and accumulation system of signals 22 is shown in more detail in FIG. 2 includes an analog-to-code converter (ADC), an arithmetic device, autonomous memory,

0 display (high-resolution graphic monitor) with the possibility of observing various sections of the autonomous memory of the DSPC (i.e., different parts of the signal), a device for outputting signals to the plotter, a control device and a communication channel with a computer All DSPC units except the communication channel with computers made in the standard CAMAC. Technical data of digital registration system:

0 - the maximum number of registration cycles - 10;

-minimum execution time of the averaging algorithm is 4 μs;

-memory of memory used for registration 5 -1K-64K 32-bit words;

- the number of bits of the ADC - 9 plus a sign; - input voltage range - + 4V, The powerful amplifier 23, which controls the current in the magnetic field sweep coils, is a powerful differential amplifier with a large depth of negative current feedback (8C dB), which ensures its linear change at the output depending on a linearly varying voltage of a triangular shape at the input supplied to the DSCNS. The amplifier 23 is designed for inductive load operation.

As can be seen from FIG. 3, the spurious signal in the inventive device (Fig. 36, curve 1) is comparable to the useful signal from an aqueous solution of nitroxyl radical (HP) at a concentration (Fig. 36, curve 2), while in the prototype device, the spurious signal (Fig. Za, curve 1) exceeds several times the signal from the HP solution even at a concentration of 5 JM (Fig. Za, curve 2). This demonstrates a decrease in the value of the spurious signal by 4 orders of magnitude and, accordingly, an increase of 4 orders of magnitude of the sensitivity of the claimed device with respect to the prototype

From FIG. 36 (curve 1) it is seen that the spurious signal in the device is comparable in magnitude with the input noise of the receiver. This confirms that the sensitivity of the device is close to theoretical

FIG. 4 is the result of an experiment whose purpose was to determine the quantitative content of impurities of ferromagnetic metals at which the spurious signal arising from these impurities would not exceed the level of input thermal noise of the receiver. The experiment was performed with the following specific values of the receiver parameters: the temperature of the input active element is Tn 293K, its noise factor is FO 2.8 dB, the passband is A f0 1 Hz, the amplitude of the alternating field on the surface of the element under test was - Nu 158 Oe

In FIG. 4, the spurious signal to noise ratio is given in dB, and the impurity concentration (in percent) along the abscissa axis is given on a logarithmic scale. From FIG. Figure 4 shows that the direct dependence of the value of the spurious signal on the logarithm of the concentration of impurities crosses the direct S / N 1 at the point Ig (Sp.%) - 5.96. Therefore, the necessary limitation on the concentration of impurities for S / N 1 is Sp. $ 1.1 (determination accuracy of about 10%).

For other values of the parameters T, F, D f and Hi, the maximum allowable value of impurities is determined by the formula SPr. Ј А xHi (Т Af F) 1, which follows from the dependence of the input noise of the receiver and the value of the spurious signal on these parameters

from the amplitude of an alternating magnetic field. The value of A in this formula is determined from the obtained experimental data for specific values of the parameters of the receiver and Nu:

etc.

N

10 -

10

-AND

(293-1 -2.8)

Thus, the restriction on the content of impurities of ferromagnetic metals takes the form: SPr. 9.6 NG2 (T-D f F) 1/2.

Since existing methods for determining the elemental composition of the material (such as activation analysis or X-ray fluorescence method) do not allow determination of the content of Fe and Ni impurities in copper at and below, the following verification procedure has been selected. Coil 3 is wound from a copper wire (MOB copper, Fe - 4 Ni - 2 - OST content 16.0.505.008-73). The ratio of the spurious signal from it to the input noise of the receiver is measured in a certain frequency band (in our case, D f0 1 Hz). Then, a coating of thickness D i is made of very pure copper, the impurity content of which is 3 10% and the spurious signal from which is below the level noise. This results in attenuation of the signal from impurities in the starting material of the coil due to the attenuation of a high-frequency alternating field at the location of these impurities. Since the spurious signal is proportional to the amount of impurities, i.e., their concentration, the attenuation of the signal by shielding the field can be converted to equivalent attenuation by reducing the concentration of impurities. This gives a point on the plot of the signal to noise ratio S / N for the spurious signal versus the concentration of impurities. Then, the thickness of the coating layer increases to a value of D2 and a new point is obtained. Several points were filmed. The intersection of the obtained curve with the asymptote - direct S / N 1 gives the maximum concentration of impurities, which allows the values of the spurious signal to be no higher than the noise level of the receiver in the working frequency band (1 Hz) and thereby approach the theoretically achievable sensitivity. (The sensitivity of any device is determined in a standard way, by the signal-to-noise ratio 1 in the working frequency band). Used verification technique with

galvanic coating with a layer of pure copper of the starting material of the coil, at the same time allows controlling the purity of the coating layer according to the law of the decrease in the value of the spurious signal with increasing thickness of the coating layer,

The evaluation of the content of impurities in the pure coating material in this procedure is as follows. The electrolyte (standard: 70 g / l H2S04 + 250 g / l CuSO / i 5Н20 + 10 m / d C2HsOH) was prepared from CuSO4 SHzO qualification of ChP (Fe and Nic $ 2 content), twice recrystallized, which gives a reduction in impurities of not less than 10 times, i.e. their content as a result of recrystallization: Fe $ 10% and Ni 2. In addition to tbgo, during precipitation from solution, due to the difference in standard electrode potentials in aqueous solutions relative to n.a. (Cu / Cu2 + is UfCu24) + 0.337 V; for Fe / Fe3 + it is U (Fe34}, 036 V and for Ni / Ni2 + it is U (Ni24) .25 V - Galvanic coatings in mechanical engineering. Handbook, vol. 1, M., Engineering, 1985, p. 25 ), we have a theoretical difference in the precipitation of Fe3 + iron with respect to copper Cu2 + exp {e U (Fe34) -U (Cu24) l / kT} - 3.9 (for Fe2 + U (Fe24, 44 V and this difference is 44) and Ni with respect to Cu Cu exp {e U (NI24hl (Cu24), 2 10 11 For example, galvanic deposition is used to refine copper. Under normal conditions (without taking additional measures, such as dedusting and using a semi-permeable baffle at the anode to prevent entry into astvor slurry of the resulting at the anode) obtained assured reduction of impurities on the order of three, i.e., the impurity content in the coating: Fe, Ni 2.

Although the dependence of the value of the parasitic signal on the content of impurities of ferromagnetic metals was determined in one element of the high-frequency part, the requirements for the content of impurities in other elements are the same if high-frequency currents of the excitation frequency of the same magnitude as in coil 3 flow in them (respectively, by these currents the same high-frequency magnetic fields are created on the surface of these elements).

Thus, in the proposed device for studying the magnetic properties of substances by connecting additional elements and special design of the main elements, the spurious signal is reduced by 80-90 dB, which leads to an increase in the sensitivity of the device by four orders of magnitude. Specified Technical

The advantages of the device also lead to an increase in the information content and reliability of research.

Claims (3)

SUMMARY OF THE INVENTION 1. A device for studying the magnetic properties of substances, containing a direct current electromagnet with magnetic field sweep coils, in the pole gap of which there is an ampoule for the test sample and a high-frequency inductor connected in parallel to a serial circuit in the form of an inductor with a coupling loop and a capacitor tuning to the frequency of the second harmonic, a high-frequency generator, the output of which is connected to the input of the communication element, a tuning capacitor at frequencies at the first harmonic, the first output of which is connected to the first output of the high-frequency inductor and a common bus, a high-pass filter, a receiver, a digital signal recording and accumulation system, and a power amplifier, the output of which is connected to the sweep coils of the magnetic field of the DC electromagnet, are connected in series the conclusions of the communication coil of the inductance coil of the serial circuit are connected to the inputs of the high-pass filter, and the high-frequency coil and inductor of the series This circuit is made with thermal stabilization systems, characterized in that, in order to increase the sensitivity, it is equipped with a parallel circuit in the form of an air inductance with a thermal stabilization system and a capacitor connected between the second terminals of the high-frequency inductor and the capacitor for tuning to the frequency of the first harmonic, the terminals of which are also connected with the outputs of the communication element, moreover, the high-frequency inductor and the inductor with a loop of communication in series circuit air-conditioned, thermostabilization systems are made with heat shields, and the high-frequency inductor, inductors and series and parallel capacitors, the coupling element, the first harmonic frequency tuning capacitor, the connecting conductors and the inner surfaces of the heat shields of thermostabilization systems are made with a conductive coating , the SPr content of impurities of ferromagnetic metals and the thickness A of which satisfy the Spr conditions. -Ј 9.6 NG2 (T D f l  F) D 2 / (a -ju o)}} 1/2 where Hi is the amplitude of the high frequency magnetic field on the surface of the corresponding element, Э; T is the temperature of the input active element of the receiver, K; F is the noise factor of the first active element of the receiver, dB; A f is the receiver bandwidth, Hz; D is the thickness of the conductive coating, m; electrical conductivity of the conductive coating, fi is the magnetic permeability of the conductive coating, GN / m; (o is the cyclic frequency of the first harmonic, rad / s. 23 MIND lt and. l SG per sample Cj 2, Pop device, 1, characterized in that the communication element is made in the form of a capacitive divider, the middle and extreme points of which are connected to the inputs and outputs of the communication element, respectively. 3. The device according to claim 1, characterized in that the ampoule for the test substance is made of a dielectric material with a tangent of dielectric angle tg0 losses and the Sp content of impurities of ferromagnetic metals satisfying the conditions   F) 1 tg 0 «5 Ref Ј 9.6 10 Hf2 (T. cw2 w -U-t 10 22 M 2 IO-4 I / M $ 5 60 70 cc .to 10 100,200 FIG. Behind H0 (e) FIG. 36