Revolution counter using magnetic domain-curved conductors that are looped and self-contained

Description

[0001] The invention relates to revolution counters using magnetic domain wall conductors which are wound in a loop-like manner and are designed to be closed in themselves, which are to be used in particular in revolution counters for larger revolution numbers U (U > 100).

[0002] Magnetic sensors can detect properties of a magnetic field, such as its field direction. One example is an angle sensor. Other types of magnetic sensors can determine how often a magnetic field has rotated. Such revolution counters can be formed, for example, by a GMR revolution counter or a TMR revolution counter, which are well known state of the art (e.g., RSM-2800: https: / / www.novotechnik.de / fileadmin / user_upload / pdfs / kataloge_flyer / Flyer_RSM-2800.pdf). The basic principle of such magnetic revolution counters is based on the use of magnetic domain walls that move in continuous magnetic regions, which can be considered magnetic conductors. They are made of soft magnetic metallic materials. The readout principle uses magnetoresistive effects.This requires, at least locally, additional magnetic and non-magnetic layers that allow the magnetic domain walls to be localized. Such revolution counters are technically realized in an electrically and magnetically continuous magnetic conductor, which is itself part of a GMR stack or locally forms a TMR stack. Magnetic domain walls move within a spirally arranged magnetic conductor due to externally acting magnetic fields generated, for example, by rotating permanent magnets. The length of the magnetic conductor increases disproportionately to the number N of turns that comprise the spiral, since the length of each individual turn increases towards the outside.If the length of the innermost loop is L 1 and the distance between the individual turns is a, the length L i of the i-th turn of a spiral consisting of N turns is given by the following formula: Length L(i) = L 1 + 8(i-1) - a. Thus, the total length L(N) of a spiral with N turns is the sum of the individual lengths L i , which is L(N) = N · L 1 + 4 · a · (N 2 < -N). This length L(N) therefore increases more than linearly with N.

[0003] As the length of the continuous magnetic conductor increases, the probability that a defect is present in the conductor that impedes the movement of the magnetic domain walls to such an extent that its function is no longer fulfilled increases proportionally. Thus, with increasing N, the yield decreases disproportionately. At the same time, the required chip area becomes increasingly larger with increasing N, primarily due to the number of contact points required for readout, the number of which increases directly proportionally with N. These properties limit the use of an open-ended spiral for the implementation of a revolution counter in practice to N <= 64. In technology, there are many requirements where significantly more than 64 revolutions must be counted, which cannot be achieved with the basic principle described above.

[0004] As proposed in DE 10 2013 018 680 A1, the revolution counting can also be implemented in such a way that, in contrast to the use of just one open spiral, several closed loops CL i (CL = closed loops) are used, whereby the i-th loop consists of a spiral with N i turns. In all spirals N i, the outer and inner ends are connected to one another and thus each form a closed loop CL i . In addition, the loops N i with i = 1.. 4 are each designed to be coprime to one another according to patent DE 10 2013 018 680 A1. This allows a revolution counter designed in this way to count from 1 to N 1 ·N 2 ·...N n . In an exemplary case, this means that for n = four loops with N i = 5; 7; 9 and 13, revolution numbers up to 4095 can be determined. The total length of all closed loops corresponds to a single spiral, according to the solution described above with N=34.

[0005] This makes it clear that due to the significantly smaller total number of individual loops in each of the loops CL i, the total length of all loops can also be made much shorter. This also means that for such a realization of a revolution counter, the total length of the magnetic conductor, which determines the yield, is significantly shorter. At the same time, this proposal also reduces the number of connection pads required for reading the respective revolution information. This also means that this revolution counter has a smaller surface area and can therefore be manufactured more cost-effectively. To realize the closed loops CL i, the inner and outer ends of all loops CL i must be connected to each other. There are two approaches described in the prior art for this. In DE 10 2013 018 680 A1, it is proposed to realize the connection by, as in Fig. 1shown, introduces a new functional element, namely a crossing within the magnetic pathway.

[0006] For this solution, the entire rotation sensor is located on one level. This solution has the advantage that the intersection can be created using the same technology step used to create the spiral. The disadvantage of this proposed solution, however, is that in the area of the intersection, the width of the magnetic conductor must be reduced to at least 1,414 times the value (diagonal D of the two webs with the width w, which defines the intersection area in Fig. 1form) and thus assumes the value range from w to D exp within the structure. Important properties of the sensor, namely the field range in which it can count without errors, are directly linked to the geometry. For error-free functionality, there is a minimum field B min , which must not be undercut in order to always transport the domain walls safely in the domain wall conductive paths. Likewise, a field B max must not be exceeded, otherwise further domain walls will develop uncontrollably within the structure. Since the values for B min and B max are indirectly proportional to the width w, this leads to a local reduction of the values for the minimum induction B min and the maximum induction B max at the intersection with the value of the width increased by a factor of 1.42, at which the revolution sensor can be operated. This is in Fig. 2There, the size of the magnetic window ΔB is shown as a function of the stripe width w. For a spiral with a stripe width w=350 nm, the magnetic window ΔB is shown by the dotted double line in Fig. 2 marked. If w increases to 525 nm, the magnetic window ΔB is characterized by the vertical double-dashed line. Since the spiral with a crossing contains structures with w=350 nm and w= 525 nm, the magnetic window ΔB results as in Fig. 2 drawn as the vertical distance between the two parallel horizontal lines. This means that a rotation sensor with crossing can only be detected within the Fig. 2 shown significantly narrower Δ B range, which is formed by the smaller value of B max and the larger value of B min of the two substructures.

[0007] The difference between B min and B max represents the width of the magnetic window in which the revolution counter can be used. Fig. 2 In the case shown, the magnetic window ΔB would be reduced from a width of 15 mT (an open spiral with a b=350 nm) to a width of just under 5 mT if it were possible to realize a crossing with a diagonal D of 525 nm. Then the magnetic window would be, as in Fig. 2 represented by the rectangle, limited by the B max value for D=w=525 nm and the B min value for w=350 nm and reduced from 15 mT to 5 mT compared to the spiral without crossing. In the known realized loops, as shown in Fig. 1 shown, the geometry of the intersection (cf. Fig. 1, circle A2) deviates from the ideal geometry (circle A1). Due to the rounding at the intersections, the value of D increases. With the larger value D exp compared to the value D of the ideal intersection, the experimentally achievable magnetic window with a size of 1 - 2 mT is even smaller than one would expect from Fig. 2 with 5 mT and therefore completely unsuitable for practical application.

[0008] The magnetic window should be as large as possible for application-technological reasons, as this window determines the sensor's immunity to interference fields. A narrow magnetic window requires additional, significant technical effort (not described in detail here) to suppress impermissible magnetic interference fields, and thus high costs and larger sensor system designs. At the same time, a narrow magnetic window requires tight tolerances in the manufacture of the revolution counter regarding installation position and tight tolerances for the magnet 12 generating the rotating field, as described in Fig. 3 for a possible use case, which in turn leads to increasing costs.

[0009] Furthermore, a crossover-free closed loop structure was proposed in patent DE 10 2010 022 611 B4. This solution requires that the short circuit of the spiral, i.e., the connection of the inner and outer ends of the spiral by a magnetic conductor, be designed in such a way that no crossing occurs. This can only be achieved by establishing this connection in a plane E2 above or below the plane E1 in which the non-closed spiral is located (see FIG. Fig. 4 and 5). If, in the ideal case, the width of the magnetic conductor is constant everywhere, this version of the revolution counter with closed loops would have the same wide magnetic window as the spiral and would therefore result in a significantly wider magnetic window than is possible in principle with the crossing variant described above. However, there is currently no known technical implementation of the latter solution. This is because this proposed solution assumes that the spiral, which is still open in level 1, is used, as in Fig. 4 in plan view and in Fig. 5 shown in cross-section, with an additional magnetic conductor M2 running from level 1 via level 2 back to level 1, which connects the two ends of the open spiral located in level 1 at the designated points K1 and K2.

[0010] The thickness of the layer structure responsible for the movement of the magnetic domain walls (the domain wall conductor) is t. The cross section on the left in Fig.5 shows that the connecting area marked M2 is partially located in a plane E2 above, or in an equally possible solution, below, the plane E1 in which the spiral to be crossed lies and thus does not touch it. Only at the points K1 and K2, where M2 meets M1, are the two structures located on a common plane E1.

[0011] The challenge of this approach is that, firstly, the short circuit must ideally be designed such that the cross-section of the magnetic conductor M2 forming the short circuit is identical to the cross-section of the magnetic conductor M1 of the spiral. This would be relatively easy to achieve in terms of manufacturing technology. Particularly critical in this approach is the point where the magnetic conductor M1 and the magnetic conductor M2 meet. This must be done with practically no offset laterally and vertically, since, as has been found, even displacements transverse to the stiffener in the range of 15 nm strongly promote the pinning of the moving magnetic domain walls and thus the value of the Fig. 2shown lower magnetic window B min. Therefore, in order not to noticeably impair the lower magnetic window, the lateral offset must be less than 1 / 20 of the width of the magnetic conductor, which in the sensors used so far is approximately 350 nm. Even more critical is the requirement that the thickness at the point where both conductors M2 and M1 directly abut each other may only differ minimally from the thickness of the adjoining conductive track sections M1 and M2 in order to obtain a continuous magnetic conductor that has the same properties over its entire length that are crucial for the sensor function for the formation of the magnetic domain walls as well as their movement through the magnetic conductor. This requirement, however, excludes a conceivable overlap at the connection point, as shown in the enlarged circle A6 in Fig. 5 shown.

[0012] The Figures 1 to 5represent solutions according to the known state of the art and the problems arising therefrom.

[0013] The invention is based on the object of specifying a revolution counter using magnetic domain wall conductors which are arranged in a loop-like manner and are essentially located in one plane and are designed to be closed, which does not have the disadvantages of the described solutions of the prior art or only to a much lesser extent, in particular it should be technologically manageable and have the largest possible magnetic window.

[0014] The invention is achieved by the features of the first claim, wherein the connecting region in which the inner and outer loop section ends of a loop of a first magnetic domain wall interconnect M1 are brought together is bridged by a second magnetic domain wall interconnect M2, the connection of which to the magnetic domain wall interconnect ends of the spiral is effected via a gap 201 each, wherein the gap 201 creates a local interruption of the domain wall interconnect M1 to be closed, wherein this gap 201 is given a width such that upon movement of a domain wall DW from a first domain interconnect section (M2 or M1), a stray field is generated therein and leads in the direction of movement after the gap 201 in the adjoining domain interconnect section (M2 or M1).wherein the average width of the gap 201 is set smaller than the thickness t of the domain wall conductive path M1 and the adjacent domain conductive path sections (M2 or M1) are covered by a non-magnetic layer S1 in the gap region.

[0015] Advantageous embodiments are the subject of the subordinate claims.

[0016] The essence of the invention is to design the magnetic interconnection path in which the magnetic domain walls move, not as a continuous, continuous interconnection path, as is usual in the prior art, but as in the Figures 6 to 14 In particular, at the transition points from the domain wall interconnect M1 to M2, a narrow gap 201 is to be provided according to the invention, which gap can be filled, for example, with non-magnetic material, as shown in the Figures 9 to 11is indicated by way of example. The interruption of the magnetic conductor has been found to result in surprising advantages that lead to an improvement in the magnetic properties of the revolution counter compared to previously known solutions. As was found in micromagnetic simulation calculations carried out, a gap 201 that is not too large within the magnetic conductor unexpectedly does not represent an obstacle to the functionality of the sensor. How the movement of a magnetic domain wall DW across the gap according to the invention takes place is described in Fig. 7 clarified.

[0017] The sequence of images in Fig. 7shows a schematic top view of the magnetization distribution in M1 and M2 as a domain wall passes through gap 201. The top image shows the initial configuration. The magnetization in both regions M1 and M2 points to the left. The narrow gap 201 between M1 and M2 is captured by a stray field that runs from the right to the left conductor.

[0018] If a homogeneous field, essentially pointing to the right, acts on this arrangement with a domain wall DW in the left conductor M1, represented by the bold arrow 13 (generated by the Fig. 3 shown outer magnet 12), the domain wall DW is moved to the right within the left conductor M1. All elements marked with (1) in Fig. 7The marked subfigures describe a movement of the domain wall in the conductor M1. The domain wall moves under the influence of a sufficiently large magnetic field towards the gap 201. There it disappears on the right side of the left conductor (marked with (2)), which leads to a change of the stray field in the gap. Together with the external field, generated by the Fig. 3 permanent magnet 12 shown and in the Figure 7 Represented by the bold arrow, the altered stray field leads to the nucleation of a domain wall DW (marked with (3)) at the left edge of the right conductor M2. This domain wall moves further to the right under the influence of the field (marked with (4)) in the right conductor.

[0019] The disappearance of the domain wall on one side and the nucleation on the other side prevents the domain wall from being held in place, as would be observed in a continuous magnetic conductor, according to the state of the art described above, at a real interface between M1 and M2 without a gap.

[0020] The following exemplary embodiments serve to explain the invention in detail. They show: Fig. 1: a top view of a spiral in which the inner and outer ends are connected in the plane of the spiral. The intersection K1 is shown twice enlarged on the right. A1 shows the idealized conditions of the intersection geometry. A2 shows the state that can usually be achieved with optical lithography and which leads to an enlarged intersection area (diagonal D exp ); Fig. 2: a representation of the dependence of the upper and lower magnetic windows (B max (w) bold black curve and B min (w) thin black dashed curve) as a function of the width w of the domain wall conductor, in which the magnetic domains move. Horizontal lines delimit the ΔB range in the case of the closed spiral with intersection with a ridge width of 350 nm and a diagonal of the intersection of 525 nm; Fig.Fig. 3: a top view of a schematic representation of a revolution counter (without showing the contacts) with four closed spirals for counting 3, 5, 7, and 11 revolutions, capable of counting up to 1155 revolutions. Above or below the closed spirals is a permanent magnet 12 rotating around the rotation axis X, whose stray field covers all four closed spirals; Fig. 4: a top view of a spiral for counting five revolutions, closed by the area M2. On the right, the circular areas marked in the left-hand image are shown enlarged; Fig. 5: a cross-section in the BB direction of . Fig. 4 . On the right, the circular area marked as K2 in the left image is shown enlarged in two versions (A5 idealized variant and A6 overlapping variant);

[0021] The Figures 1 to 5 represent the known or conceivable state of the art. Fig. 6 shows a cross-section of the domain wall interconnect with a gap 201 according to the invention between M1 and M2. On the right, in section A5, a transition between M2 and M1 with a gap in between is shown enlarged. Fig. 7 shows sequences of the movement of a domain wall DW from one side of the magnetic conductor M1 across the gap 201 according to the invention to the other magnetic conductor M2. The position of the domain wall DW is schematically shown by a black ellipse, the direction of magnetization within the magnetic interconnects M1 and M2 by black arrows. The thick arrow represents the magnetic field acting on the structure from the permanent magnet 12. Fig. 8 shows a cross-section of the connection point M1 to M2 with gap 201. On the right, a complete XMR stack (GMR or TMR) is shown with M1 as the magnetic interconnect, below which a separating layer 101 (e.g.: 2 nm Cu for a GMR stack and ∼ 1 nm insulator for a TMR stack), including a so-called artificial antiferromagnet 102, consisting of CoFe / Ru / CoFe and an antiferromagnet 103; Fig. 9 a cross-section of a design of the contact point, in which the edges of the layers M1 and M2 are formed obliquely and are geometrically spaced from each other by a separating layer S1; Fig. 10 a cross-section of a design of the contact point between M1 and M2 with a gap in between, in which the edges of the layers M1 and M2 are formed obliquely and in a V-shape (cf. bevels marked in bold in Fig. 11) and are geometrically spaced from each other by a separating layer S1 and S2. a plan view of a design of the contact point, in which the edges of the layers M1 and M2 are formed obliquely and are geometrically spaced from each other by a separating layer S1; Fig.Fig. 12 shows a cross-section of the contact point, showing a vertical offset of the size vs of the two domain wall conductors; Fig. 13 shows a top view of the connection, showing a lateral, horizontal offset hs of the two domain wall conductors; and Fig. 14 shows a top view of a connection in which materials with different saturation magnetization M s (1)< and M s (2)< are used for M1 and M2.

[0022] The Figures 1 to 5 represent the known or conceivable state of the art, which has already been adequately described in the introduction along with the associated disadvantages.

[0023] Away Fig. 6 begins a detailed description of the present invention. Fig. 6A section of the cross-section of the domain wall interconnect with a gap 201 according to the invention between the domain interconnect sections M1 and M2. On the right, in section A5, a transition between M2 and M1 with the gap 201 in between is shown enlarged.

[0024] How the propagation of a domain wall DW takes place in the two magnetic conductive path sections and across the gap 201 is shown Figure 7 in detail. The position of the domain wall DW is schematically represented by a black ellipse, and the direction of magnetization within the magnetic domain wall pathways M1 and M2 is indicated by black arrows. The thick arrow represents the magnetic field generated by the permanent magnet 12 (cf. Fig. 3 ) magnetic field acting on the structure. How domain wall transport occurs across the gap 201 according to the invention has already been described in detail above.

[0025] Figure 8The right-hand part shows a typical structure, as is known and used for a GMR or TMR stack. Layer 103 denotes an antiferromagnetic layer, e.g. PtMn, and the layer 102 lying on top of it denotes an artificial antiferromagnet AAF (artificial antiferomagnetic layer). This is a layer system known as an artificial antiferromagnet and typically has a CoFe / 0.8 nm Ru / CoFe structure. Layer M1 is the layer in which the magnetic domains move within the aforementioned loop. It is usually soft magnetic and consists of Ni, Fe and / or Co alloys such as Ni 81 Fe 19 , NiFeCo, NiFeB, CoFe, CoFeB or combinations of these materials. According to the present invention, there is now the proviso that layer M1 is not directly connected to the layer or layer stack that forms M2.

[0026] Figure 9shows an example in which layer M1 and layer M2 are separated by a non-magnetic separating layer S1, shown hatched. According to the invention, this layer consists of a non-magnetic material and can be electrically conductive, semiconductive, or insulating. This allows for a great deal of variability in technological implementation. Fig. 9 the contact point where the edges of the layers M1 and M2 are oblique but parallel to each other and are geometrically spaced from each other by a separating layer S1.

[0027] How Figure 10shows, the lateral distance between M1 and M2 does not have to be constant within the scope of the present invention, but can also vary, as in the case of the V-shaped gap shown there. In this technical solution, both areas are beveled in the vertical direction, provided with a minimum distance by a separation layer S1, and then covered with a separation layer S2 that completely fills the gap. For this solution, too, the two separation layers S1 and S2 can be made of any non-magnetic materials. Non-magnetic means they must not have a permanent magnetic moment, i.e., they must be neither ferromagnetic nor ferrimagnetic. This means that these materials must be diamagnetic, paramagnetic, or antiferromagnetic.

[0028] The gap between M1 and M2 can also be arranged obliquely in the plane, as shown in Fig. 11is shown as an example in a top view of the domain wall interconnects. Combinations of various previously described embodiments of the gap geometry are also within the scope of the invention.

[0029] A great advantage for the technological implementation is that the solution according to the invention allows that the cross sections of M1 and M2 do not have to merge exactly into each other, but can be slightly offset both laterally and vertically, as in Figs. 12 and 13 indicated by way of example.

[0030] Fig. 12 shows as an example the cross-section of the contact point, where a vertical offset of the size vs is allowed. As long as the vertical offset vs is below 25% of the thickness t of the domain wall conductor M1, i.e. with a typical thickness of the soft magnetic layer of 40 nm below 10 nm, the magnetic domain wall can be Fig. 7schematically shown, skip this gap. The same applies to a lateral offset hs of the two structures M1 and M2, as shown in Fig. 13 As long as the lateral offset hs is less than 25% of the width of the domain wall interconnect, i.e., in a typical system, 360 nm below 90 nm, the magnetic domain wall can bridge the gap between M1 and M2 as described above.

[0031] The proposed solution offers further technological degrees of freedom, of which examples are Fig. 14a solution is shown in which the value of the saturation magnetization of the two regions M1 and M2 is different. The magnetic flux acting from M1 to M2 and from M2 to M1 is crucial for the functioning of the movement of the magnetic domain wall through the gap according to the invention. This means that the product of the cross section times the saturation magnetization M s should be approximately the same. For example, for the formation of the domain wall interconnect region M2, a material with a 40% higher value of the saturation magnetization M s (2)< compared to the value of the saturation magnetization M s (1)< can be used if the cross section of this material is reduced by 40%. This results, for example, when the domain wall interconnect M1 made of Ni 81 Fe 19 with a saturation magnetization of 800 kA / m is combined with M2 made of CoFe with a saturation magnetization of 1140 kA / m.This reduction can be achieved either by reducing the width or the thickness by 40%, or by a combination of both, such as reducing the width by 20% and the thickness by 20%. However, when reducing the width and thickness geometries, a symmetrical reduction is preferable to a strongly asymmetrical reduction.

[0032] From the micromagnetic simulations performed, it can be deduced that the expected values for B min and B max remain virtually unchanged as long as the mean gap width is < 50% of the layer thickness t of the magnetic conductor. If the mean gap width increases significantly above this value, a moderate increase in B min and a moderate decrease in B max can be expected. At the maximum permissible changes in the mean gap width, relative to the layer thickness t, the width of the magnetic window decreases from 15 mT to 10 mT.

[0033] The implementation of the proposed invention enables a novel method for producing a closed loop by bridging a spiral-like arrangement in one plane with a known structure suitable for revolution counting with a structure supporting the domain walls in a second plane, using a geometric interruption. The present invention offers a number of previously unavailable possibilities for technological implementation and, if successfully implemented, leads to a significant widening of the magnetic window compared to previously known prior art solutions.

[0034] While in the case of transitions, as is usual in the prior art (cf. e.g. DE 10 2010 022 611 B4), even with the smallest steps or lithography defects in the order of 15 nm, a pinning of domains can be observed, which leads to the inoperability of the revolution counter, a comparatively large interruption of the domain wall conductive path at the location of the gap according to the invention has no negative influence on the domain wall transport. List of reference symbols

[0035] E1Plane in which the loop-like domain wall interconnects lie E2Connecting plane K1, K2,Intersection points A1, A2, A3, A4, A5, A6Circles with enlarged images wWidth of the domain wall interconnect M1 DDiagonal of an intersection D exp enlarged (realistic) value of D XAxis of rotation of the permanent magnet 12 DWDomain wall 12Permanent magnet 13Arrow indicating field direction B-BSection plane M1Domain wall interconnect of the loop-like structure M2Second bridging domain wall interconnect M s (1)< , M s (2)< different saturation magnetizations tThickness of the domain wall interconnect M1 201Gap between M1 and M2 101Separation layer 102Artificial antiferromagnet 103Antiferromagnet S1Non-magnetic layer vsvertical Offset between M1 and M2 hhorizontal offset between M1 and M2

Claims

1. A multiturn counter comprising domain wall conductors which are arranged in the manner of closed loops and are situated substantially in a plane (E1), thus forming a spiral, the connecting region, in which the inner and outer loop section ends of a loop of a first magnetic domain wall conductor (M1) are combined, being bridged by a second magnetic domain wall conductor (M2), characterized in that their connection to the magnetic domain wall conductor ends of the spiral is made with a respective gap (201), the gap (201) creating a local interruption of the domain wall conductor (M1) to be closed, this gap (201) being provided with such a width that, during a movement of a domain wall (DW) of a first domain wall conductor section (M2 or M1), a stray field is generated therein and, in the movement direction downstream of the gap (201), results in nucleation of a domain wall (DW) in the subsequent domain wall conductor section (M2 or M1), the mean width of the gap (201) being set to be less than the thickness (t) of the domain wall conductor (M1, M2) and the adjoining domain wall conductor sections (M2 or M1) being encompassed by a non-magnetic layer (S1) in the gap region.

2. The multiturn counter according to claim 1, characterized in that domain wall conductor sections (M1, M2) are allowed to have a horizontal and / or vertical offset (hs, vs) with respect to one another as long as these offsets are less than 25% of the thickness (t) or the width (w) of the domain wall conductor (M1).

3. The multiturn counter according to claim 1, characterized in that the end faces of the domain wall conductors (M1, M2) forming the gap (201) are disposed parallel to one another and / or obliquely in an angular range of 25° to 90°.

4. The multiturn counter according to claim 2, characterized in that the end faces of the domain wall conductors (M1, M2) forming the gap (201) are disposed parallel to one another and / or obliquely in an angular range of 25° to 90°.

5. The multiturn counter according to claim 1, characterized in that soft magnetic materials having differing saturation magnetizations are used for the first and second domain wall conductor structures (M1 and M2), the difference in the saturation magnetizations advantageously to be kept below 40%.

6. The multiturn counter according to claim 5, characterized in that the deviation of the product of cross-section and saturation magnetization of the two soft magnetic regions of the domain wall conductor structures (M1 and M2) is <25%.

7. The multiturn counter according to claim 1, characterized in that the non-magnetic layer (S1) consists of a diamagnetic, paramagnetic or antiferromagnetic material.