SU1654872A1 - Magnetooptical method for detecting vertical bloch walls at band domain tips - Google Patents

Abstract

The invention relates to computing and can be used in the development of drives on vertical Bloch lines (LEDs). The aim of the invention is to increase the reliability and expand the field of application of the method by determining the number of VBL in the top of the band domain. The method is based on the excitation of vibrations of VBLs fixed at the bend of domain boundaries, and allows the detection of VBLs both in the tops and cylindrical magnetic domains and at the bends of the domain boundaries of the labyrinth domain structure. If there is no VBL in the apex, then in the swinging planar field the domain boundary remains stationary. If a higher number of VBLs are present at the top of the band domain, the area S increases. At frequencies Ј / l / qe (H / v - ns), the amplitude of the oscillation plots exceeds the linear resolution limit of the magneto-optical means, therefore the value of S is proportional to the number of VBLs at the top of the band domain. 1 il. i /

Description

The invention relates to computing and can be used in the development of drives on vertical Bloch lines (VBL).

The aim of the invention is to increase the reliability and expand the field of application of the method by determining the number of VBL in the top of the band domain.

The drawing shows the top of the band domain (PD) d of the swinging magnetic field H + H at different times, top view (the direction of magnetization in the center of the domain boundary is indicated by arrows}

in the center of the VBL, the magnetization perpendicular to the plane of the domain boundary, the region S occupied by the oscillating domain boundary, is shaded.

In accordance with the proposed method, detection of VBL in the apex, PD is carried out as follows.

The magnetic film is affected by a constant plenary field and an alternating magnetic field perpendicular to the PD boundary, and the amplitude H and the period T of the alternating magnetic field are set in accordance with the expression

T (,

where Nc is the coercivity field,

HZ - mobility of the domain boundary

q 0 is the linear resolution limit of the magneto-optical means. Illuminate a portion of the film containing the top of the PD with polarized light, record the magneto-optical signal and judge the VBL number by the amplitude of the variable component.

The proposed method is based on the excitation of vibrations of VBL fixed at the bend of domain boundaries, and allows the detection of VBL in both vertices and in the CMD and bends of the subfloors of the labyrinth domain structure.

If there is no VBL in the top, then in the swinging plenary field the domain boundary remains stationary,

 If a greater number of VBLs are located at the top of the DC, then the area S is

h (And it is. At frequencies N Ј --- (

qO

the amplitude of the oscillating sections exceeds the linear resolution limit of the magneto-optical means, therefore the value of S is proportional to the number of VBLs in the upper band of the band domain. VBL detection at frequencies large

than --- (Hi - IL), difficult, by q0

How much is the useful magneto-optical response comparable to the noise of a measuring device?

I

The variable signal component is

the response recorded by the photodetector is proportional to the value of S. Calibration of a specific photodetector for a given frequency of the alternating field H provides a direct determination of the number of VBLs at the top of the AP.

Example. The magnetically uniaxial (Y, Bi) g (Fe, Ga) fO, 2 film with a thickness of 9.8 μm with the parameters 4fiM 120 Oe, Hc 0.5 Oe, Q 25, oi 0.3, C

0

f.

..

five

0

five

Q

0

five

 10 cm / s contains a band domain. At the top of the AP, a constant plenary field H, 123, directed along the PD, is fixed by VBL. A variable planar field H 4.5 E with a frequency of 35 KHz, perpendicular to the action potential, causes an oscillation of VBL. The film is placed in a standard MIN-8 polarization microscope and illuminated with polarized light from an LG-72 laser. The diameter of the light spot in the top of the PD is 5 microns. The signal-response is recorded with a photodetector device OES-51 and amplified with a selective amplifier U2-8. The magnitude of the signal-response from 1 VBL 75nxV, from 3 VBL 180 JUV.

Claims (1)

Invention Formula The magneto-optical method of detecting vertical Bloch lines at the top of a band domain based on a magnetic film acting on a constant plenary magnetic field directed along a band domain by an alternating magnetic field, illuminating a portion of the film containing the top of the band domain, polarized light and then registering the magneto-optical signal, characterized in that, in order to increase the reliability and expand the field of application of the method by determining the number of vertical fleas The lines at the top of the band domain, the magnetic film is affected by an alternating magnetic field perpendicular to the border of the band domain, and the amplitude H and the period T of the alternating magnetic field are set in accordance with the expression q0 // U, where HC is the coercivity field, the mobility of the domain boundary, q 0 is the linear resolution limit of the magneto-optical means, and the number of vertical Bloch lines at the top of the band domain is judged by the amplitude of the variable component of the magneto-optical signal. t-0 H- And + -t l-j Ј.