The switchable memory element

 

(57) Abstract:

The invention relates to the field elements of automation and computing, in particular for magnetic thin-film memory and switching elements. The aim of the invention is to expand the functional capabilities of the storage element. This goal is achieved by the fact that located above the strip center conductor 9 applied in relation to it so that the magnetic field from leaking in it current coincides in direction with the axis of easy magnetization of a thin-film magnetoresistive layers 5, 6, and thin-film magnetoresistive layers 5, 6 have different values of the field magnetic anisotropy and the ratio of the larger field magnetic anisotropy smaller is at least four. 2 C.p. f-crystals, 4 Il.

The present invention relates to the field elements of automation and computing, in particular for magnetic thin-film memory and switching elements.

Known magnetoresistive memory (see U.S. patent N 4751677, G 11 C 11/15) using anisotropic magnetoresistive (AMR) effect, on the basis of the two-layer magnetic films FeNiCo with semiconductor shchina effect, equal (2-3)% and, as a consequence, a sufficiently high demands on technology to obtain acceptable signal reading.

Known (see J. M. Daugthon. Magnetoresistive memory technology. Thin solid films, 216, 1992, p. 2705-2710) a storage element on the spin-valve magnetoresistive (SVMR) effect, we adopted as the prototype of the proposed technical solutions, designed as a multi-layer strip with the main part of the two magnetoresistive films of Fe15Ni65Co20separated by a layer of copper. When SVMR the effect of the change in resistance depends on the angle between the vectors of magnetization of adjacent magnetic films separated by a layer of copper, and not on the angle between the vectors magnetized magnetic film and flowing through her current, as in the AMR effect. The second feature SVMR effect is that the maximum difference of the resistances of the magnetic films corresponds to the parallel and antiparallel to the location of the vectors of magnetization of adjacent magnetic films, in contrast to the perpendicular position between the vectors of magnetization and current for the AMR effect. The minimum resistance corresponds to the parallel arrangement of the vectors of magnetization magnetic is th effect. Value SVMR effect on samples with films of Fe15Ni65Co20about 42% for 10 magnetic layer at room temperature (J. M. Daugthon and Y. J. Chen. GMR materials for low field applications. IEEE Trans. Magn. v.29, N6, p. 2705-2710). However, to use SVMR effect it is necessary to paramagnetically only one magnetic film of the two. To do this, increase the coercive force of one of the magnetic films due to the exchange interaction with additional magnetic film, for example, FeMn film. In the above-mentioned storage element uses two film FeNiCo, and in his description not specified the way to obtain films with different values of magnetic anisotropy or coercive force. The rapid increase obtained SVMR effect occurring at the present time, due to the large amount of ongoing developments in the world in this area of research, leading to the possibility of using structures based on the memory element with SVMR effect as switching elements due to the presence of such patterns of threshold characteristics.

The aim of the invention is to expand the functional capabilities of the storage element by giving it the properties of a switching element.

Phnom effect, containing a silicon substrate on which are successively located the first insulating layer at least one 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 easy magnetization and located between the thin-film layer of copper, the second protective and insulating layers, conductive layer with a Central conductor passing over the strip, and the third protective layer, the specified center conductor is perpendicular to the axis of easy magnetization of thin-film layers of strips, and thin-film magnetoresistive layers of the strips have different values of the field magnetic anisotropy. In this respect a large field magnetic anisotropy smaller coincides at least four strip may contain multiple structures, each of which includes two thin-film magnetoresistive layer and located between the thin-film copper layer, and the element itself may consist of several parallel connected stripes.

Salient features of the above together, leading to magnicifent thin-film magneto-resistive layer strips and execution of thin-film magnetoresistive layers with different values of the field magnetic anisotropy.

The essence of the invention lies in the fact that the proposed structure provides the storage element threshold characteristics, it can be used as a switching element with memory at low drive currents. Threshold characteristics, as shown by the following calculations appear in structures in which the direction of the magnetic field from flowing in the current conductor coincides with the direction of the axis of easy magnetization (old) magnetic films, while in the storage elements is perpendicular to the direction of the magnetic field of the conductor and on. The use of magnetoresistive layers with different values of the field magnetic anisotropy eliminates the need for additional FeMn film to increase the coercive force of one of the magnetic films due to the exchange interaction, the introduction of the same into a strip of several structures of the magnetoresistive layers, separated by layers of copper, dramatically increases the spin-valve effect. The use of multiple parallel-connected strips can increase the current element (the current through the strips) to a value sufficient to control the next element. This allows with the tion is illustrated by drawings, where in Fig. 1 shows the structure of a switching element on SVMR effect in the context of Fig. 2 topology strips with two structures of the two magnetoresistive layers separated by a layer of copper; Fig. 3 topology element with two parallel strips of Fig. 4 design characteristics of the switching element of Ie(ICR)/UPete=onst, where Iethe current through the strip, ICRthe current through the conductor, UPetethe voltage applied to the strip (item) for (a) UPete27 mV and (b) UPete108 mV when the resistance strips 270 Ohms, the ratio of the length of the strip to a width of 3 for the case when an directed along the strip.

A switching element with a memory for SVMR effect contains (Fig. 1) the silicon substrate 1, on which are positioned successively the first insulating layer 2, a strip with pointed ends, consisting of two protective layers 3, 4, two magnetoresistive magnetic layers 5, 6 and a copper layer 7. On top of the strips are positioned successively insulating layer 8, the conductive layer 9 with the Central conductor and the second protective layer 10. In Fig. 2 shows the topology of a strip containing two structures with magnetoresistive layers. The strip consists of two protective aqueous layer of copper I1, separating structure. The topology element with two stripes (Fig. 3) includes two parallel connected conductors 12, 13 strips 14, 15 and passes over the strips 14, 15 of the Central conductor 16.

The work of the switching element depends on the direction on magnetic films relative to the strips. There are two cases: an directed along or across the strips. Let us first consider the method used for estimating the characteristics of a switching element with memory, based on theory of micromagnetism.

Calculation of the parameters of the element is carried out in two stages determine the distribution of the magnetization in both the Mr films depending on magnetic fields generated by currents control, and process variation from the condition of minimum energy (E) system of two magnetic films and, further, calculation of the signals read (USCfor data touch currents read (ISaint) and the external magnetic field (HNR).

We used a model in which the distribution of the magnetization is read constant along the Mr film, which is a rather rough approximation. One of the important consequences of this approximation will overestimate the calculated values of the fields once the Noi film (Minand discounttravel magnetic film (Mn) from the edges of the strips, which reduces the values of these fields.

The energy of the system of two Mr films equal

E Ek+ Em+ Er+ Eh< / BR>
< / BR>
where

Ekenergy azonitrile, Emmagnetostatic energy, Erthe interaction energy of two Mr films, Ehthe energy in the external magnetic fields, including fields from the touch current, H HNR+ HSaintKin,nthe magnetic anisotropy constants of the upper and lower magnetic films,in,nthe thickness of the Mr film,in,nthe angles between ALN and Minand MnHpinnfield demagnetization occurring at the edges of the stripes:

< / BR>
whereininthe surface density of magnetic charges on the edges of the film.

Search for Emin(in,nis brute force under given initial conditions Minand Mn.

An directed along the strips. Work switchable element is as follows. We believe that in the initial state in the absence of current through the strip of the magnetization in the two magnetic films 5,6 are antiparallel to each other. Recorded in the item information is otnositelno strips. The recording media is feeding into the Central conductor current of a certain polarity. To reduce the magnitude of the write current possible supply of striped additional current of a certain polarity. Work element as a switching is illustrated by the calculated characteristics (Fig. 4), obtained, for greater clarity, when the value SVMR effect 200% for the case when an magnetic film is located along the strip, and the Central conductor across. Value SVMR effect only affects the differential currents between the closed and open States. The control node in the element is a conductor, the control is flowing in it current. The characteristic element in the switching mode is hysteretic, with distinct thresholds switch. The switching element is carried out by the magnetization reversal discounttravel magnetoresistive film under the action of the magnetic field created by the current in the Central conductor 9. After the termination of the current in the Central conductor discountcanada film is not over magnetize in the opposite condition, which determines the hysteresis characteristics. When the supply current reverse polarity discountcanada film pen is magnetic films 5, 6 does not lead to the destruction of recorded information, because "O" or "I" is determined by the direction of the magnetization vector vysokorentabelnoy film, which is not over magnetize when the switching element. The state with antiparallel directed vectors of magnetization of the magnetic films corresponds to the maximum resistance of the strips, i.e., when this element is in the "closed" state, and the state with parallel arrangement - minimum resistance strips, i.e., when this element is in the "open" position. The hysteresis element with an along the strip means storing information due to the stability of both States discounttravel film in the absence of currents control without destroying the information defined by the direction of the magnetization vector vysokorentabelnoy film. This creates new functionality to the application of the proposed element, for example, as logic elements. The presence of the strip several structures of low and vysokooleofobnyh magnetoresistive layers separated by a layer of copper, does not change the physics of the item, and also leads to an increase SVMR effect. In the structure with several parallel connection is leave a manifold increase in the current element, it can be used to control the next element.

It is evident from Fig. 4 shows that for this version of the element with increasing UPetethere is a reduction of the switching threshold. This is because the increase of the current flowing through the magnetoresistive layers currents leads to an increase in the deflection angle of the magnetization vector discounttravel film from an that facilitates switching of magnetization. However, increasing the deviation of the magnetization vector from an leads to a decrease in the differential resistance between the closed and open States, i.e. there is an upper limit UPetefor the element.

An directed crosswise strips. This option has a number of differences from the above:

1. Threshold characteristics flatter, i.e., a complete switching occurs when several large drive currents. This is due to significantly large demagnetizing fields, which leads to profitability gradual deviation of the magnetization vector discounttravel magnetic film.

2. There is a reverse effect depends on the switching current from the supply voltage, since the magnetic fields generated by flowing in the magnetic films currents will be prepjatstvovanie with two parallel along an vectors of magnetization in this case is unstable due to large values of demagnetizing fields.

To create a high magnetic anisotropy can be used alloy Fe15Ni65Co20used in magnetoresistive memory elements and which allows to obtain the value of the field magnetic anisotropy up to 20 e, and with increasing cobalt content up to 30% of the field magnetic anisotropy reaches 40 E. To create the same layer with a small amount of field magnetic anisotropy can be used permalloy Fe20Ni80giving the magnitude of the field magnetic anisotropy from 2 to 5 E.

Thus, the claimed switching element with a memory for SVMR effect has a threshold characteristics and memorization, which allows to extend the field of application for use in logic circuits, etc., One of the promising applications of such elements use in single-chip magnetoresistive storage devices with random sampling of controls.

1. Switchable element with memory on the spin-valve magnetoresistive effect containing a silicon substrate on which are successively arranged first insulating layer, a strip containing two protective layers separated by at least one structure consisting of two who between them thin-film layer of copper, the second insulating layer, a conductor layer with a Central conductor passing over the strip, and the third protective layer, characterized in that the Central conductor is perpendicular to the axis of easy magnetization of the magnetoresistive film strips, magnetoresistive film have different values of the field magnetic anisotropy, and a larger field magnetic anisotropy smaller is at least four.

2. Item under item 1, characterized in that the strip contains several structures, consisting of two magnetoresistive films and located between the thin-film layer of copper, separated by a thin-film layers of copper.

3. Item under item 1, characterized in that it contains several parallel strips.

 

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