SU370561A1 - METHOD OF MEASUREMENT OF MAGNETOTRICTION OF THIN MAGNETIC FILMS - Google Patents

Description

one

The invention relates to a technique for measuring the magnetic properties of ferromagnetic samples of small cross sections, to methods for measuring the magnetostriction of thin magnetic films, and can be used in the development of equipment for monitoring the parameters of thin magnetic films.

A known method for measuring the magnetostriction of thin magnetic films is as follows. The test sample is placed in the high-frequency test field of the sensor (measuring coil), directed along the axis of easy magnetization of the film. The sample is subjected to (magnetization reversal) of a low-frequency sinusoidal field, directed along the axis of the difficult magnetization of the film. The signal taken from the sensor is detected, amplified and fed to one of the oscilloscope inputs. The other input of the oscilloscope receives a signal proportional to the magnitude of the low frequency field. The magnetostriction of the film is determined by the magnitude of the magnetoelastic parameter (constant). To do this, the melsd | m distance from M.aiKCHiMyMBMiH is measured by the permeability of the pulse, obtained on the oscilloscope screen, in the undeformed and deformed states of the sample. Further calculations allow us to determine the magnetoelastic parameter and the film magnetostriction.

The known method is characterized by low measurement accuracy, which is due to the use of an oscilloscope and the need to measure linear dimensions on its screen. The measurement error in this way is ± 10%. In addition, the impossibility of automating the measurement process increases the measurement time and does not allow this method to be used for multiple or continuous monitoring.

The purpose of the invention is to improve the measurement accuracy and automate the process of measuring the magnetostriction of thin magnetic films.

To do this, according to the proposed method, a low-frequency field directed along the axis of the hard magnetization of the film creates a linearly increasing or linearly decreasing with respect to the average value and transforms the dependence of the film permeability on the low-frequency field into a time dependence. The signal taken from the sensor is then differentiated and converted into a square wave signal, which is re-differentiated. From the signals thus obtained, a control signal is selected that corresponds to the transition of the sensor signal through the maximum value, which, after a delay, is used to change the direction of the low-frequency field. The magnetostriction is judged by the increment of the average value of the low frequency field arising from the deformation of the sample.

FIG. 1 shows a block diagram of a device implementing the proposed method; in fig. 2 - graphs explaining the transformation of the dependence of film permeability along the axis of easy magnetization on the floor along the axis of difficult magnetization: |, l / () in the time dependence | a, l / (0; in Fig. 3, time diagrams explaining proposed measurement method.

The dependence of the magnetic permeability of the film along the easy magnetization axis on the field along the hard magnetization axis Yat (see Fig. 2a) has a maximum when the field along the hard magnetization axis is equal to the anisotropy field of the Yak film. If the field along the axis of the difficult magnetization of the film changes linearly, making it incremental or decreasing, as shown in FIG. 1 b, the permeability of the film | 1l / (0 changes over time and the law shown on fit. 1 0. This dependence | l, l f (0 is periodic and has maxima at time (, tz, ts, t , in which the linearly varying field Yat is equal to the anisotropy field of the film / (Yat). Such a conversion is based on (0 in MeUnooo; head, and | oimo C: Tb M.) (0 carried out yugg in the proposed method of measuring magnetostriction of thin magnetic films. It allows subsequent operations on the signal from the sensor, since this signal is a function of time.

FIG. 1 shows a block diagram of a device implementing the proposed measurement method.

The sample under study or a portion of the film sample was placed in the high-frequency field of sensor 2 and a low-frequency homogeneous field created by the first roll of the field; The roller 3 is powered by a controlled source 4 of a linearly varying current. The average value of the linear current in the coil 3 is measured by the device 5 of the magnetoelectric system. Sensor 2 is powered by a high-frequency current measuring the increments of the inductance of sensor 6, the signal of Skotorgo is fed to the first differentiating device 7. The output from the first differentiating device is fed to the driver 5, and from it to the second differentiating device 9. The output signal from the last is fed to the delay circuit 10 and after it is the current source control device 11. The signal from the control unit is fed to the input of current source 4 and changes the direction of change of the output current of the source.

A method for measuring the magnetostriction of thin magnetic films is as follows.

The film sample is placed in the high-frequency field of the sensor and in the low-frequency field. The low frequency field is created to vary linearly and transform the dependence of film permeability on this field into time dependence. As the low-frequency field Yat rises from zero (see Fig. 3, e), the permeability of the film | Yal also increases (see Fig. 3, a). At time ti (see Fig. 3), the low-frequency field becomes equal to the anisotropy field of the film I, and the permeability of the film (Ll reaches its maximum value (see Fig. 3, a). A further increase in the low-frequency field leads to a decrease in the permeability of the film. So As a sample of the film is placed in the sensor 2 field, the inductance of this sensor, as well as the output signal of the sensor increment inductance meter, changes according to the same law as the film permeability, i.e., the input of the differentiator 7 is signaled (see FIG. . 3, a) The signal is differentiated by the differentiating device 7 p (see Fig. 3.6), which is converted by the shaper 5 into a square-shaped signal (see Fig. 3, c).

At time i, the signal at the output of the differentiator 7 is zero, and at the output of the imaging unit 8, the polarity of the output signal changes to the opposite. The output signal of the imaging unit 8 is subjected to re-differentiation by the device 9 and receive a signal (see Fig. 3, d), which is detained "with a pair of g (see Fig. 3, d).

FIG. 3, e, only negative polarity signals are shown, which are used as control signals. Thus, at the time point + ts, a signal from the output of the delay circuit 10 is supplied to the device P to control the current source. The output signal from this device affects the controlled source 4 of a linearly varying current. At time 2 (see Fig. 3, e), the direction of change of the current changes, and the field Yat - the current and field begin to decrease.

Starting from the moment of time tz under the influence of the decreasing floor Yat (see Fig. 3, e), the permeability of the film of the CL begins to increase (see 3, a).

The process is repeated. At time 4, a control signal is produced (see Fig. 3, d), and at time 4 / 4H-4, the field Yt again changes the direction of change — it increases. The process is then repeated.

Thus, the field Yt will vary linearly, i.e., increase or decrease in relation to its mean value. The average value of this field is equal to the anisotropy field of the Yak film.

The magnitude of the average value is measured with a magnetoelectric system, which is calibrated directly in the field values.

In order to measure the magnetostriction in the sample, deformation is created in various ways depending on the particular sample being tested. It can be created, for example, by applying a tensile or compressive force, or by bending the substrate on which the film is applied. When a sample of a film is deformed, its anisotropy field changes. This leads to a change in the average value (increment) of the low frequency field Yat. By the sign of the increment of the mean value of the field Ya.sr, the sign of the magnetostriction of the film is judged, and by the value of the increment - of the magnitude of the magnetostriction. The sign and magnitude of the increment of the field is counted directly on the device 5, included in the source circuit of the field. Subject of the Invention A method for measuring magnetostriction of thin magnetic films with uniaxial anisotropy in a magnetoelastic parameter by acting on a test film sample of a high frequency test field directed along the axis of easy magnetization of the film, and a low frequency field directed along the axis of difficult magnetization of the film, so that measurement and automation of the measurement process, the low-frequency field creates a linearly increasing or linearly decreasing with respect to its mean frontier edge value and convert dependence Neg ogaitsaemosti film from the low-frequency field in the time dependence; the signal taken from the sensor is differentiated and converted into a signal of a regular waveform, which is re-differentiated; from the received signals, a control signal is selected that corresponds to the transition of the sensor signal through its maximum value, which after the delay is used to change the direction of the low-frequency zero and an increment in the mean value of the low frequency field arising from the deformation of the sample is judged on magnetostriction.

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