SU554514A1 - Method for controlling the uniformity of cylindrical thin magnetic films and apparatus for carrying out the method - Google Patents

Description

and the second output of the phase detector is connected to the second input of the first adder. FIG. Figure 1 shows a graph of the amplitude and phase increments of the third harmonic voltage of the secondary emf. from changes in thickness and saturation induction of the magnetic layer of the film; in fig. 2 is a block diagram of an installation that implements the proposed method for controlling the uniformity of cylindrical thin magnetic films along their generatrix. The magnetization curve of a section of a cylindrical thin magnetic film along the generatrix (along the axis of difficult magnetization) can be represented as a broken line, the first section that passes through the origin of coordinates at an angle, and the second is parallel to the x-axis. The intersection of both sections occurs at the point with the coordinates I / ,, BS (Hh is the anisotropy field, BS is the induction of saturation). When a sinusoidal field is applied to the film, its reversal occurs along the axis of difficult magnetization, and the induction (Bs) in the film changes in accordance with the magnetization curve according to a harmonic law only in a linear portion of the curve. In the second part of the curve, the induction in the film yr varies according to a harmonic law and its composition contains the highest odd harmonics, of which the third amplitude has a maximum amplitude. In the composition of the secondary emf magnetizing current also harmonic components appear. The expression for the amplitude of the voltage of the third harmonic of the secondary emf. has the form .. 16i..lO- "A f4 / rf l- (Yf (1) JJ where / is the frequency of the magnetization reversal current; Etg is the amplitude of the third harmonic voltage; L is the number of turns of the secondary winding of the magnetizing device; BS is the induction of saturation magnetic film; R is the radius of the wire substrate; d is the thickness of the magnetic film layer; I / i is the anisotropy field of the film; Hm is the amplitude of the magnetizing field. The expression for the instantaneous value of the voltage of the third harmonic of the secondary emf can be written as ,., „, Sin (w, + tv) where is the initial phase shift. From expressions 1 and 2 it can be seen that at the same time In this case, the variation of the thickness d and the magnetic induction of the 5s sections of the film along the length of the test sample, the amplitude and phase of the third harmonic voltage of the secondary emf are functions of the variables tp, (d, 5) and t t, (and, B ,) at f const and Яй Я ", the nominal values of the thickness of the nominal and magnetic saturation induction Bs correspond to the amplitude and phase of the voltage of the third harmonic of the secondary emf, Eot, and 1 |) o (Fig. one). The possibility of separately determining the thickness d and the magnetic induction of saturation of the Ss plots of the CTMP sample under investigation in length is based on the different nature of the variations in the amplitude and phase of the voltage of the third harmonic of the secondary emf. when changing the thickness and magnetic induction of parts of this sample along the length. If we use the coordinate system (E), then a small change in the parameters Ad and ABs correspond to straight line segments located in the (oj), E plane, respectively, at angles Φ1 and Φ2 to the E axis (Fig. 1). With this in mind, the system of equations (3) can be represented as En, -Eot, + / "lAa cos -fi -j- / WjAS cos pa, (jj), -f- t, Ly sin (fi -f sin" pa , (4-) where Ad and ABs are, respectively, positive increments of thickness and magnetic saturation induction of a portion of the CTMP sample under investigation; mi, m2, / Pz and OT4 are scale factors having dimensions from, 5 / µm, those, d / r, those , degrees / μm, t degrees / G. If the amplitude of the voltage Е-т is multiplied by the coefficient т4з1пф2, and the phase of this voltage is multiplied by the coefficient / Пгсозф2, then the difference obtained after the conversion of signals depends only on the increments the magnetic layer of the controlled area of the CTMP, i.e. (Et, Eot,) t sin 9, - (;) - ф,) / Яа cos cf, d (sin "fa cos cpj - m, n, sin f cos ( p,), W - M (Sin, COS f 1 - - / ttjOT, sin piCos (f,. (5) Similarly, the difference of signals can be obtained, depending only on the change in magnetic induction, i.e. SW, - A5 sin, cos pi - - / and, yes, sin cf,. The coefficients are calculated as follows: the amplitude (Eot,) and phase (p) of the third harmonic of the secondary harmonic are measured. ds, corresponding to the nominal thickness () of the magnetic layer and nominal induction and saturation (Bs of the CTMP reference sample section; the amplitude (d) of the third harmonic of the toric emf measured by the known thickness ( d) the magnetic layer and the nominal saturation induction (B) of the CTMP reference sample section; the amplitude ("„ BS and phase (r13d) of the voltage third of the secondary emf harmonic, corresponding to the nominal thickness () of the magnetic layer and known induction of saturation (Bs) of the CTMP control sample area; determine the amplitude and phase increments of the third harmonic voltage of the secondary emf from the change in the thickness (Ad) of the magnetic layer and the saturation induction of the areas of the control samples of the CTMP, d Em, d - Earn ;; - to EmA Eom, - d), ; calculate the coefficients t, COS p, LI. "BSDFY ffl.COSep rr:; FROM, Sin cf, Determining the increment of the thickness of the magnetic layer (Ac) of the saturation induction (ABs) of the sections of the monitored CTMP samples relative to the nominal thickness values (Other ) and saturation induction (Bs) are made in the following order: the amplitude (Et,) and phase (ij) is measured; the voltage of the third nd harmonic of the secondary emf; From the expressions (5) and (6), the required values of At and ASs are determined, which can be determined from the graphical construction (Fig. 1). For this, the amplitudes and phases of the third harmonic voltage of the secondary emf are measured. according to expressions (1-5) to calculate the coefficients. According to the measured values of the amplitudes and phases of the third harmonic voltage of the secondary emf. In the selected scale, the points O, B and C are plotted on the graph. Through the points O and B, OE C, straight sections are drawn, which are the directions of change of small increments of the thickness (M) of the magnetic layer and the saturation induction (A5s) of the sections CTMP samples; measure the amplitude (Et,) and phase (f) of the third harmonic voltage of the secondary emf. corresponding to the thickness (d) of the magnetic layer and the saturation induction (ABs) of the areas of the test sample; according to the measured amplitude values (Et,) and phase (f) of the voltage of the third harmonic of the secondary emf. point L is plotted on the graph; straight points are drawn through point A and parallel to the segments OV and OC; the points of intersection of straight line segments drawn through point A with straight line OM and OS segments are projected onto coordinate axes; from the segments cut off on the coordinate axes, the corresponding increments of the amplitudes of the amplitudes (L /; „„ y AE ,,,, B) and flz (A-fi and Afd) of the third harmonic voltage of the secondary electromotive force are determined; increments of the thickness (Ad) of the magnetic layer and saturation induction (ABs) of the samples of the CTMP samples are determined from the expressions or M MZ sin It nil COS fl OR D5, -f t cos cp2 "4Sin 2" The device contains a series-connected sinusoidal voltage generator 1, amplifier 2 power, pass-through sensor 3, consisting of a long primary winding and a short secondary winding, a selective amplifier 4, the output of which connects a series-connected amplitude detector 5 and a first adder 6, and a series-connected phase detector 7 and a second su Matrix 8. The output of the first adder b is connected to one input of the registration unit 9, to the other input of which the output of the second adder 8 is connected. The second output of the amplitude detector 5 is connected to the second input of the second adder 8, and the second output of the phase detector 7 to the second input of the first adder 6. The device operates as follows. Using an oscillator 1, power amplifier 2 and sensor 3, an alternating sinusoidal field is created which transmutes the test areas of the film by placing a sample of a cylindrical thin magnetic film in the sensor hole until saturating along the hard axis. From the voltage of the secondary winding of the sensor 3, the selector1; harmonic amplifier 4 is amplified and amplified. Voltage of the third harmonic of the secondary emf from the output of the selective amplifier 4 enters an amplitude detector 5 and a phase detector 7. After detection, the stress levels corresponding to the memorial values of the thickness fifuoM and the BS saturation induction of a cylindrical thin magnetic film are compensated by reference voltages, and the voltage levels corresponding to increments of the thickness Arf and saturation induction ABs of the CTMP sections are multiplied by the coefficients and from the outputs of the detectors 5 and 7 are fed to the inputs of adders b and 8. From the output of the amplitude detector 5 connected by tion with the input of the first adder b enters voltage multiplied by t431if2 coefficient and a second output of the amplitude detector 5 connected to the second input of the second adder 8 is supplied the voltage multiplied by the coefficient m, G. From the output of the phase detector 7, connected in series with the input of the second adder 8, the coupling multiplied i.i; i coefficient / nicostpi, and from the second output

the phase detector 7 connected to the second input of the first adder 6 is supplied with a voltage multiplied by

t2SOZf2.

In the adders 6 and 8, these voltages, previously multiplied in the detectors 5 and 7 by the corresponding coefficients, are added together.

Voltage depending only on changes in the thickness d of the CTMP section from the output of the adder 6 is applied to one input of the registration unit, and voltage depending only on changes in BS saturation induction of the CTMP section from the output of the adder 8 to the other input of the recording unit.

Measured values in the recording unit that depend only on the change in the thickness Ad and only on the change in the saturation induction ABs of the CTMP sections according to graphs or tables, are converted into measured thickness and saturation induction films or measured on the recording unit dial gauges .

Before measurements are started, the device is tuned to the CTMP reference samples in the following order.

A sample of the CTMP with nominal duoM thickness and BS saturation induction is placed in the opening of sensor 3. The reference voltages in the detectors 5 and 7 compensate for the voltages corresponding to the nominal values of thickness and saturation induction, and the readings of the dial gauges of the recording unit are set to the required values.

A sample of the CTMP is placed in the opening of the sensor 3 with a nominal thickness value rfjioM and a known saturation induction value BS, different from Bs. The voltage at the second output of the phase detector 7 is set at the output of the adder 6, the voltage corresponding to the readings on the dial gauge of the registration unit of the nominal thickness of the sample CTMP.

A sample of a CTMP with a nominal value of saturation induction H5 "o" and a known thickness d different from is placed in the opening of sensor 3. The voltage at the second output of the amplitude detector 5 is set at the output of the adder 8, the voltage corresponding to the indications of the dial gauge of the registration unit of the nominal saturation induction 5s „of the CTMP sample. By changing the voltage value at the first output of the amplitude detector 5, the voltage at the output of the adder 6 corresponds to the readings of the dial gauge of the recording unit of a known sample thickness of the CTMP.

A sample of a CTMP with a nominal thickness value flfnoM and a known BS saturation induction value different from Bs is placed in the sensor 3 opening. The voltage at the first output of the phase detector 7 is set at the output of the adder 8, the voltage corresponding to the indication of the gauge of the known induction unit sample saturation CTMP. By changing the voltage value at the second output of the phase detector 7, the voltage value at the output of the adder 6 is adjusted.

If necessary, the described operations are repeated.

Changes in the voltage values to the required values at the outputs of the amplitude detector 5 and phase detector 7 when setting up the device using control samples of the CTMP are the steps of experimentally determining the corresponding coefficients and multiplying the detected third amplitude and voltage of the third EHD voltage on them. received at the input of the detectors 5 and 7..

Claims (2)

1. A method for controlling the uniformity of cylindrical thin magnetic ilenok along the generatrix by magnetizing them with an alternating field and measuring the amplitude of the third secondary emf harmonics, characterized in that, in order to simplify separate control of individual parameters of film sections, the amplitude of the alternating magnetizing current is fixed, the amplitude and phase of the third harmonic voltage of the secondary emf are converted. proportional signals are subtracted from them the components corresponding to the increment of individual parameters. 2. A device for carrying out the method of claim 1, comprising a sinusoidal voltage generator, a power amplifier, a pass-through sensor and a selective amplifier connected in series, and a recording unit, characterized in that it is equipped with a series-connected amplitude detector and a first adder, as well as sequentially connected by a phase detector and a second adder, and the input of the amplitude detector and the input of the phase detector are connected to the output of the selective amplifier, the output of the first adder is connected chen to one input of the registration unit, and the output of the second adder is connected to another input of the registration unit, the second the output of the amplitude detector is connected to the second input of the second adder, and the second output of the phase detector is connected to the second input of the first adder. . From, / /one  I "