Magnetic inverter

 

(57) Abstract:

The invention relates to elements of automation and computing, in particular for magnetic thin-film memory and switching elements. The invention allows to create the logical elements on the basis of the spin-valve magnetoresistive structures for operation under severe operating conditions. The inverter contains a silicon substrate. On the substrate sequentially arranged first insulating layer, a strip with pointed ends. The strip contains two protective layers separated magnetoresistive layers and thin-film copper layer. On top of the strips is second insulating layer, the conductor layer with the conductor feedback, the third insulating layer. 1 C.p. f-crystals, 3 ill.

The present invention relates to elements of automation and computing, in particular thin-film magnetic logic elements.

Known logic elements (LE) based on semiconductor (I.e. Budinski. Logic circuits in digital technology.- M: Communications, 1977) and magnetic (H.P. Vasiliev, B. P. Petrukhin. Design of logic elements. -M.: Energy, 1970) technologies. Despite the prevalence is evident and is named temperature range, the lack of resistance to radiation effects. Existing magnetic logic elements do not allow the integral manufacture and their use is limited by low complexity schemes, mainly for work in difficult conditions, where the specific advantages of the magnetic elements are crucial.

Currently, much attention is paid to the development of items based on the "giant" magnetoresistivity, and, first and foremost, the creation of Mr memory elements (MRSA) for integral storage devices with random access (NVR) on the basis of SVMR structures. The main advantages of magnetic elements: non-volatility, radiation resistance, non-destructive and read a wide temperature range, new Mr thin-film elements in addition to high performance plus the ability chip (together with a semiconductor frame) integral performance. With the rapid progress in the production of structures with a high value SVMR effect occurs an interest in the possible use of such structures as LAYE. First of all such elements could be applied in an integrated single-chip Mr NVR as the panel is Loy/MCl/HM/MCh/OC/protective layer

where

MCland MCh- two ferromagnetic layers made of Co, Ni or NiFe and separated by a layer of nonmagnetic metal HM - Cu, Ag, Au or other MCl- free film with a smaller field of magnetization reversal, MCh- fixed film with a large field of magnetization reversal. As OS (exchange layer), creating an exchange interaction with the nearest ferromagnetic layer MChfor fixing (for example, increasing the coercive force), is commonly used Fe50Mn50. This layer creates the exchange anisotropy in the layer MShbecause of which the magnetization vector Mhmay be directed only at relatively high fields (>200 - 300 e), whereas the layer MClover magnetize in weak fields (less than 20 e).

SVMR effect is that the resistance of the multilayer structure depends on the angle between the directions of the vectors of magnetization of the layers MCland MChin the neighboring ferromagnetic films separated by a layer of copper, and does not depend on the angle between flowing in the film by the current I and the magnetization vector M in this film, as in anisotropic MP (AMR) effect. When this is achieved the value SVMR effect in megol the>/P>When SVMR the effect of the maximum resistance change of MRSE corresponds to the transition from parallel to antiparallel to the location of the Mh(the magnetic film with a higher field of magnetization reversal) and Ml(the magnetic film with a low field magnetization reversal) in the adjacent magnetic films and back. To achieve this effect is to paramagnetically only one of the two adjacent films. The magnetization switching of an external field over magnetize the film with a smaller coercive force or magnetic anisotropy.

The aim of the invention is the creation of logical elements with high density on the basis of the spin-valve magnetoresistive structures capable of operating in severe service conditions.

This objective is achieved in that the magnetic inverter contains a silicon substrate on which are successively arranged first insulating layer, at least one spin-valve magnetoresistive strip with pointed ends, containing two protective layers separated by at least one structure comprising two spaced one above the other thin-film magnetoresistive layers with the axis of the light namagnichivayushchego layer of copper, the second insulating layer, the conductor feedback, passing over the spin-valve magnetoresistive stripe along it, the third insulating layer, an information guide, passing over the spin-valve magnetoresistive stripe, and the third protective layer, with the specified spin-valve magnetoresistive strip connected to the first end with a power source and a second end with the first end of the conductor located outside the spin-valve magnetoresistive strips and connected to the second end of the conductor of feedback, with the thin-film magnetoresistive layers have different values of the field magnetic anisotropy. The ratio of the larger field magnetic anisotropy smaller is not less than four, the strip may contain multiple structures, each of which includes two thin-film magnetoresistive layer and located between the thin-film layer of copper. The main feature of the above together, leading to the solution of the problem is the execution of the inverter on the basis of the multi-layered spin-valve magnetoresistive structure.

The essence of the invention lies in the fact that the proposed structure obespechivaushyi magnetic materials properties.

The invention is illustrated by drawings, where Fig.1 shows the structure of the inverter on the basis of a spin-valve magnetoresistive structure in section, Fig. 2 shows a diagram of the inverter, and Fig.3 shows the characteristic of the input-output inverter.

The inverter on the basis of a spin-valve magnetoresistive structures contains (Fig.1) the silicon substrate 1, on which are positioned successively the first insulating layer 2, SVMR strip with pointed ends, consisting of two protective layers 3,4, two magnetoresistive magnetic layers 5,6 and a copper layer 7. Over SVMR strips are consistently the second insulating layer 8, the conductor layer with the conductor feedback 9, the third insulating layer 10, an information conductor 11 and the third protective layer 12. Next to SVMR strip is connecting SVMR strip with guide feedback conductor 13, a protective layer 14. Schematically the inverter consists (Fig.2) from SVMR strips 15, which is connected by a conductor 16 with guide feedback 17 and passing over the strip 15 information guide 18.

Let us first consider the method used for calculation of the characteristics of the inverter based on theory of micromagnetism.

The model calculation about the rotation angles of the vectors of magnetization of the magnetic films SVMR sandwich from magnetic fields, created by the magnetization of the magnetic film element, and the touch (Is) and information (Isig) currents, from the condition of minimum energy systems (Ies). Search for Emin(i) , where i- the angles of the magnetization vectors of all magnetic tapes, MRSA is brute force under given initial conditions Mi. In the analysis used a simplified model of the distribution of magnetization in the film, based on the assumption that the volume of each of the magnetic film in the direction of the vector M have the same direction. The application of this model leads, in the first place, to some overestimation of the values of the demagnetizing field acting on the magnetic film in comparison with the real, i.e., to increase energy and decrease system stability. In the result decreases the upper bound of the range of current control signal and reading, as well as for a number of variants increases the lower bound currents account due to the blocking of the process of magnetization reversal demagnetizing fields. Thus, the actual area, in our opinion, must be greater than estimated.

When calculating the energy system, we consider energy: magnetic anisotropy, magnetostatic, demagnetizing fields neighboring the LASS="ptx2">

For PE calculations of the dependence of the resistance of the structure R and touch current from the supply voltage and from the information of the current Isigfor a given topological and magnetic element parameters:

R=f1(U,Isig)

Is=f2(U,Isig)

where

f1and f2- defined functions magnetic and topological parameters LAYE.

The inspection criteria of stable information transfer chain of repeaters, each of which consists of a pair of inverters.

The criterion for stable transmission of information to the chain of repeaters is that the characteristic of the input-output Iout=f(Isig) repeater had three intersections with direct Iout=Isig. This condition imposes restrictions on the shape characteristics and the minimum value SVMR effect. The criterion is reduced to the following conditions:

1. The intersection region of the curve (r) means that the angle of slope should not exceed 45o< / BR>
(Iout/Isig)r> 1.

2. The intersection in the lower pane (Iout=Imin)

Imin< I1r.

3. The intersection in the upper pane (Iout=Imax)

I1r< Nie positive feedback. All this affects the threshold characteristic properties LAYE, but reduces the amount of current the magnetization reversal strips, which improves the current control LE. The reduction of the differential currents requires more careful selection of the values of b/a to perform the criterion of stable data transmission. The analysis shows that with the decrease / decrease the value of b/a.

The calculations are carried out for the magnetic structure consisting of a film of permalloy (Fe20Ni80and film Fe15Ni65Co20with different values; the width of the strips a= 2 μm; the thickness of the Mr film 5 nm; anisotropy field Hlk= 2 e and Hhk= 20 E. the Selected parameters correspond to the real opportunities of test structures. The calculations were carried out assuming that the thickness of the copper layer (Cu) less than half the thickness of the magnetic layer (m).

The inverter is as follows.

When an directed crosswise strips with a width of strips of several microns demagnetizing fields from the edges of the strips are tens of Oersted even when the thickness of the film is 5 nm or less. This leads to stability in the absence of currents control only state with antiparallel arrangement of Mhactor Mhin the absence of additional external fields is always antiparallel to the vector Ml. The guide is located above the strip along it. When working as a PE transverse conductor, wherein, when the flow and its current Iwithcreates a magnetic field along the strip, makes no sense, because switching of magnetization should be determined by the current of the conductor. Alternating magnetization is performed by the simultaneous action of currents Icand Is. First is the pulse current Isand its polarity is such that the magnetic fields generated by the touch current, pressed Mhand Mlto OLN. Submission of Icin Windows Explorer on the strip creates a magnetic field causing the magnetization reversal Ml. The final state after disabling currents will again antiparallel arrangement Mhand Ml.

It is possible that the element operates in a constant external magnetic field, peremagnichivanie Ml. Then the steady state will be parallel to the direction of Mland Mh.

The main idea of using CWMR structures as a LE - transfer and processing of information by generating a current pulse due to the differential resistance on the s to control the next element by filing in the information guide. To navigate to the schemes operated by power surges, use bridged with inclusion of PE in the shoulders of the bridge.

The ideal case for such schemes is the constant voltage mode, when all the supply voltage is connected to the strip LAYE. When this drop touch current will be maximum. Another extreme case is the constant touch current. As mentioned above, the physics of magnetization reversal processes of the strips is very different in these two cases: at a constant voltage U, is applied to the strip, the changes of the touch current when switching depending on the previous state of the strips will either increase dramatically improves threshold characteristics, or to slow down.

The basic element of all LE-based structures with SVMR effect is to strip connected at one end to a voltage source and a second end - to information to guide the next LAYE, and passing over the strip information conductor one end connected to the strip previous LAYE, and the other to the ground. In this element through the strip and the conductor is always flowing current: Iminwhen the strip element are antiparallel direction vectors Mland Mh. The vectors Mland Mhthe strip is selected so that the current flowing through the strip of touch current tends to stabilize, pressing the magnetization vector to OLN. In the opposite direction Isthe item has a poor threshold characteristics and unhealthy. But in the first case, an improvement of the threshold characteristics of the element.

To improve the threshold properties you can use positive feedback (Fig. 2), namely, that the conductor with Isinitially passes over the strip so that the generated touch current magnetic field sought to paramagnetic Ml. After that, the conductor goes to the next item. Thus, positive feedback contributes to the magnetization reversal of the strip element.

The initial state of the element with positive feedback is determined by the value of the supply voltage U. With increasing U, the growth of Is. On the one hand, this leads to stabilization of the provisions of the vectors Mland Mhand, on the other - to increase peremagnichivanie Mlthe magnetic field of the conductor with Is. For some Uminthe influence of the field from the conductor gets the directional vectors of magnetization of both films.

If U<Uthis item is a repeater, and if U>Umin- inverter. However, as the repeater, and the inverter must operate at the same voltage, we choose the inverter as a basic element of all other LAYE. In particular, the repeater can be formed from two inverters.

Consider the PR for the item with the size of the strips 24 μm2and with OLN is directed across the element. First of all we are interested in the existence of threshold characteristics and the possibility of using a given PE to perform logical operations. The calculations were performed for / = 100% .

Change R of the inverter from U in the absence of Isigand additional constant external field H0has a threshold character. The disadvantage of this option is high-field magnetization reversal Mlthat leads to the necessity of control currents in the tens of milliamps.

To significantly reduce this disadvantage can be the introduction of a constant field H0contributing to the reversal magnetization Ml. The analysis shows that the optimal value of Ho0pt= 0,5 Hhk= 10 In this H0the strip is always in condition with in parallel directional and upper values of the voltage (Umaxdue to the offset field of the magnetization reversal discounttravel film produced by the current I1rand the possibility of remagnetization of Mh. In this case, Umin= 0,1, Umax= 3,7 Century. In Fig. 3 shows the output characteristic of the inverter for Umin= 0,1 Century can be Seen that the inverter has a threshold characteristic: Imin= 0.9 mA, Imax= 1,8 mA, I1r= 1.2 mA.

Summing up: the optimal variant of the inverter is a strip running in the supply voltage range from 0.1 to 3.7 V in the presence of H0= 0,5 Hhk.

From the calculations it follows that for a = 2 μm

Umin= 0.2 V;

Umax= 0,275;

Imin= 2.0 mA;

Imax= 2,9 mA for Umin;

(/)min= 50% at b = 2.4 μm.

This minimum value SVMR effect to date has already been reached for multilayer structures, which makes the real development LAYE on SVMR structures.

1. Magnetic inverter, characterized in that it contains silicon substrate on which are successively arranged first insulating layer, at least one spin-valve magnetoresistive strip with pointed ends, containing two protective layers, separated by menichelli with the axis of easy magnetization, perpendicular to the length of the spin-valve magnetoresistive strips, and located between the thin-film layer of copper, the second insulating layer, the conductor feedback, passing over the strip along it, the third insulating layer, an information guide, passing over the spin-valve magnetoresistive stripe, and the third protective layer, with the specified spin-valve magnetoresistive strip connected to the first end with a power source and a second end with the first end of the conductor located outside the spin-valve magnetoresistive strips and connected to the second end of the conductor feedback moreover, the thin-film magnetoresistive layers have different values of the field magnetic anisotropy and the ratio of the larger field magnetic anisotropy smaller is at least four.

2. The inverter under item 1, wherein the spin-valve magnetoresistive strip contains several similar structures, separated by a thin-film layers of copper.

 

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