Classification system and corresponding method

Abstract

The invention relates to a conversion device (10) for converting an initial signal (SI) into a data set (SC) comprising a magnetic component (20) configured to vary between a first magnetic state (M1) and a second magnetic state (M2); a junction member (30) separating the magnetic component (20) between an upstream chamber (21) and a downstream chamber (23); an excitation unit (50) configured to generate a physical excitation in order to excite the magnetic material, the physical excitation being generated as a function of the initial signal (SI); a detection unit (60) configured to detect and record at least one trigger characteristic parameter (Nbf), the data set (SC) comprising said at least one trigger characteristic parameter (Nbf). The invention also relates to a classification system (1) comprising such a conversion device (10), a conversion method, and a classification method. Figure 3

Description

Title of the invention: Classification system and corresponding method Technical field of the invention

[0001] The present invention relates to a classification system for classifying an input signal into a signal class. This type of classification system is particularly suitable for applications in the development of impulse neural networks known as "in materio computing" according to the established Anglo-Saxon terminology. This refers to the use of physical devices to artificially reproduce the behavior of a neural network, using the properties of the physical device(s) considered, and in particular the material(s) they comprise.

[0002] The present invention also relates to a classification method for classifying an input signal into a signal class, this classification method being implemented by a classification system as presented previously. State of the art

[0003] There are different ways to artificially reproduce a neural network, for example in the field of photonics, or in the field of spin electronics.

[0004] Existing solutions in the field of photonics have made it possible to replicate the behavior of individual elements as well as to demonstrate the functionalities of more complete devices. However, these achievements have complex architectures and generally involve significant energy consumption.

[0005] Existing spin electronics solutions are also interesting because they have good endurance compared to photonic systems, and are compatible with CMOS technologies (for Complementary Metal Oxide Semi-conductor according to the established Anglo-Saxon terminology).

[0006] However, the various solutions are limited so far to the proof of concept of simple devices and are not suitable for the production of a functional neuromorphic device.

[0007] Document EP4160484A1 discloses such a functional neuromorphic network capable in particular of performing voice recognition of spoken digits. This network consists of a set of magnetic devices each reproducing the behavior of a neuron. In particular, these magnetic devices are configured so as to reproduce the properties of accumulation, loss or leakage, and triggering or "firing", beyond a certain threshold.

[0008] In order to reproduce a complete neuromorphic network, chambers are arranged in several rows and separated by doors, the rows all being connected to a central nucleation chamber which serves as a starting point for the propagation of a domain wall. This propagation of the domain wall then occurs when a physical excitation corresponding to the signal to be processed is generated. For this, a magnetic domain of given orientation is nucleated in the central nucleation chamber. This magnetic orientation is opposite to that of the rest of the magnetic component, which makes it possible to form the domain wall. In this configuration, the physical excitation will have the effect of exciting and moving the magnetic domain wall located at the border between two domains of opposite magnetizations.Chambers will thus be filled and doors crossed until a network is obtained in which certain chambers are in a first magnetic orientation and in which the other chambers are in a second magnetic orientation. The image obtained from the complete network is then characteristic of the information to be processed which was used to excite the system.

[0009] This solution has the advantage of allowing the processing of a signal, without having to resort to very significant computing capacities, in particular for pre-processing calculations and for the calculation of synaptic weights.

[0010] However, in order to obtain a neuromorphic network capable of discriminating a wide variety of signals, it is necessary to increase the number of chamber strings. However, given that the size of a chamber is of the order of 0.1 pm to 10 pm on each side, and that a number of strings can be greater than 10,000, the total surface area of ​​the classification system can quickly become large, or even unsuitable for certain applications.

[0011] Furthermore, the energy consumption required for physical excitation by a magnetic field increases with the surface area of ​​the device. In the case of using an electric current as the physical excitation quantity, the energy consumption increases with the length of the strings.

[0012] There is therefore a need to find a compact and low-energy solution allowing the reproduction of a complete neuromorphic network.

[0013] Object of the invention

[0014] The present invention aims to propose a solution which responds to all or part of the aforementioned problems.

[0015] This aim can be achieved by implementing a conversion device for converting an initial signal into a data set, the conversion device comprising: - a magnetic component comprising a magnetic material configured to vary locally between a first magnetic state having a first magnetization, and a second magnetic state having a second magnetization different from the first magnetization, said magnetic component being subdivided into a plurality of zones, where each zone is either in the first magnetic state or in the second magnetic state; each region in the first magnetic state being separated from a region in the second magnetic state by a magnetic domain wall; - a junction member separating the magnetic component between an upstream chamber and a downstream chamber and ensuring magnetic communication between the upstream chamber and the downstream chamber, said junction member being characterized by a magnetic transmission value corresponding to a capacity of the junction member to allow a displacement of the magnetic domain wall in a direction of propagation, said direction of propagation being defined from the upstream chamber to the downstream chamber; - an initialization unit configured to place the magnetic component in an initial magnetic configuration, in which the magnetic domain wall is arranged at the junction member; - an excitation unit configured to generate a physical excitation in order to excite the magnetic material, so as to move the magnetic domain wall in the direction of propagation, the physical excitation being generated as a function of the initial signal; - a detection unit arranged at the downstream chamber, said detection unit being configured to detect and record at least one characteristic triggering parameter at the moment when a physical parameter associated with a deformation state of the magnetic domain wall exceeds a predetermined threshold value, the data set comprising said at least one characteristic triggering parameter.

[0016] The arrangements described above make it possible to propose a conversion device capable of converting an initial signal into a set of data comprising one or more characteristic triggering parameters. This type of device is particularly suitable for artificial neuron applications. Furthermore, the use of only two chambers makes it possible to obtain a more compact conversion device requiring a lower electrical energy input.

[0017] By "magnetic transmission value" is meant the capacity of the junction member to allow the transmission of a magnetic domain wall. In other words, this "magnetic transmission value" corresponds to the inverse of a resistance that the junction member can produce on the passage of a magnetic domain wall.

[0018] By "magnetic domain wall" we mean a boundary separating two zones of the same continuous magnetic medium which are not in the same magnetic state.

[0019] The conversion device may further have one or more of the following characteristics, taken alone or in combination.

[0020] According to one embodiment, the conversion device comprises a nucleation member configured to place the magnetic component in a magnetic nucleation configuration, in which all the zones of the magnetic component are placed in the first magnetic state, with the exception of a nucleation zone which is placed in the second magnetic state, said nucleation zone being contained in the upstream chamber.

[0021] Generally, the magnetic material of the magnetic component is inhomogeneous. In other words, in most configurations, the magnetic component comprises a plurality of zones, where at least one zone of the plurality of zones is in the first magnetization state, and where at least one other zone of the plurality of zones is in the second magnetization state.

[0022] According to one embodiment, the initialization unit comprises the nucleation member.

[0023] According to one embodiment, the physical parameter associated with a state of deformation of the magnetic domain wall is a distance counted in the direction of propagation from the junction member, the characteristic triggering parameter being detected and recorded by the detection unit at the moment when this distance exceeds a predetermined threshold distance.

[0024] Alternatively, the physical parameter associated with a deformation state of the magnetic domain wall is a measurement of surface area or a ratio of surfaces, the trigger characteristic parameter being detected and recorded by the detection unit at the moment when this surface area or this surface ratio exceeds the predetermined threshold value.

[0025] According to one embodiment, the data set is a number corresponding to the number of times a trigger characteristic parameter is recorded by the detection unit. In other words, the data set is equal to the sum of the detected trigger characteristic parameters.

[0026] According to one embodiment, the excitation unit is configured to at least temporarily stop the physical excitation of the magnetic material when the following condition is verified: at least one characteristic triggering parameter is detected by the detection unit.

[0027] According to one embodiment, the conversion device further comprises a closed-contour peripheral delimitation in which the magnetic component is fully contained.

[0028] Thus, it is possible to limit the expansion of the domain wall when it meets the peripheral delimitation.

[0029] Generally speaking, the peripheral delimitation is a non-magnetic zone. For example, a groove dug by engraving in the material constituting the magnetic component, or an area having undergone irradiation by a laser beam or ion irradiation making it possible to form said non-magnetic zone.

[0030] According to one embodiment, the peripheral delimitation is quadrilateral. Thus, the manufacture of the conversion device is simplified.

[0031] According to one embodiment, the initialization unit is configured to place the magnetic component in the initial magnetic configuration when the following condition is verified: the at least one characteristic triggering parameter is detected by the detection unit.

[0032] Being able to reset the magnetic component by placing it in the initial magnetic configuration after each detection of a characteristic triggering parameter makes it possible to accelerate the return of the magnetic component to the initial magnetic configuration, which makes it possible to temporally detect a maximum number of characteristic triggering parameters by the conversion device.

[0033] According to one embodiment, the initialization unit comprises an expansion member configured to move the magnetic domain wall to the junction member, so as to place the magnetic component in the initial magnetic configuration.

[0034] Thus, it is possible to place the conversion device in a configuration where the physical excitation generated by the excitation unit only contributes to moving the magnetic domain wall beyond the junction member into the downstream chamber.

[0035] According to one embodiment, the initialization unit comprises the excitation unit, the excitation unit then being configured to move the magnetic domain wall to the junction member, so as to place the magnetic component in the initial magnetic configuration.

[0036] According to one embodiment, the conversion device further comprises a reconfiguration unit configured to modify the magnetic transmission value of the junction member.

[0037] Thus, it is possible to modify the magnetic transmission value of the junction member to adapt it to the initial signal that one wishes to convert.

[0038] According to one embodiment, the reconfiguration unit is configured to modify the magnetic transmission value of the junction member each time the detection unit detects a characteristic triggering parameter.

[0039] Thus, it is possible to modify the magnetic transmission value of the junction member at the time of placement of the magnetic component in the initial magnetic configuration. This makes it possible to artificially reproduce a succession of chambers separated by junction members having a magnetic transmission value that varies. In other words, the junction member is reconfigurable.

[0040] According to one embodiment, the excitation unit comprises a current generator configured to generate an electric current.

[0041] Synergistically, the use of a current generator as an excitation unit in a conversion device comprising only two chambers makes it possible to reduce the energy consumption of the system while maintaining good conversion quality of the initial signal by the conversion device.

[0042] According to one embodiment, the physical excitation corresponds to a signal comprising electric current pulses.

[0043] The aim of the invention can also be achieved by implementing a classification system intended to classify an input signal into a signal class, the classification system comprising: - at least one pre-processing device intended to transform the input signal into at least one initial signal; - at least one conversion device as described above and taking as input an initial signal from among said at least one initial signal and converting said initial signal taken as input, into a data set; - an identification unit taking as input the data set and configured to associate the input signal with a signal class according to the data set, said signal class being chosen from a set of predetermined signal classes recorded in a memory of the classification system.

[0044] The arrangements described above make it possible to propose a classification system capable of classifying an input signal as a function of the response detected by the conversion device.

[0045] According to one embodiment, the classification system comprises at least two conversion devices.

[0046] According to one embodiment, the classification system comprises at least two conversion devices taking as input the same initial signal or each a distinct initial signal obtained by transforming the same input signal by means of a distinct pre-processing device.

[0047] For example, the classification system may take as input a single input signal, and may include one or more pre-processing devices. The pre-processing device(s) may convert the input signal into an initial signal that is identical for all of the conversion devices, or alternatively into a plurality of initial signals that may or may not be distinct for each conversion device. In other words, the same input signal may be pre-processed differently by the pre-treatment device for each conversion device.

[0048] In this way, it is possible to perform at least two conversions of the initial signal into a data set, to improve the signal conversion.

[0049] The aim of the invention can also be achieved by implementing a method for converting an initial signal into a set of data, the conversion method being implemented by a conversion device as described previously, and comprising the following phases: - an initialization phase comprising an initial step in which the magnetic component is placed in the initial magnetic configuration; - an excitation phase in which the excitation unit generates the physical excitation according to the initial signal, so as to move the magnetic domain wall; - a reconfiguration phase implemented if the detection unit detects that the at least one physical parameter associated with the deformation state of the magnetic domain wall exceeds the predetermined threshold value, the reconfiguration phase then comprising a detection step in which the detection unit records at least one characteristic triggering parameter in the data set.

[0050] The arrangements described above make it possible to propose a conversion method making it possible to convert an initial signal into a set of data by a conversion device which can use only two chambers of a magnetic material.

[0051] It is therefore well understood that the excitation phase is implemented continuously, and that several detection steps can be implemented, in particular each time that the at least one physical parameter associated with the deformation state of the magnetic domain wall exceeds the predetermined threshold value.

[0052] The conversion method may further have one or more of the following characteristics, taken alone or in combination.

[0053] According to one embodiment, the initial signal and the physical excitation are a function of time. In this case, it can be provided that the conversion method is stopped at the time end of the physical excitation.

[0054] According to one embodiment, the initialization unit is configured to place the magnetic component in the initial magnetic configuration, for example via the expansion member.

[0055] According to one embodiment, the initialization unit comprises a nucleation member, the initialization phase then comprising a nucleation step, implemented before the initial step, in which the nucleation member places the magnetic component in the magnetic nucleation configuration in which all the areas of the magnetic component are placed in the first magnetic state, except for a nucleation area which is placed in the second magnetic state, said nucleation area being contained in the upstream chamber.

[0056] Thus, it is possible to prepare the conversion device to carry out a conversion, in particular when it has not been used for a long time.

[0057] According to one embodiment, the initial step is implemented at the same time as the excitation phase. In other words, it is the physical excitation generated during the excitation phase which makes it possible to move the domain wall towards the junction member so as to pass from the nucleation magnetic configuration to the initial magnetic configuration.

[0058] According to one embodiment, the initial magnetic configuration corresponds to a configuration where the inhomogeneous magnetic material is in the second magnetic state in the upstream chamber, and in the first magnetic state in the downstream chamber, or vice versa.

[0059] According to one embodiment, the reconfiguration phase is implemented when the magnetic material present in the downstream chamber is entirely in the second magnetic state.

[0060] Thus, the detection of the exceeding of the threshold distance by the magnetic wall is simpler.

[0061] According to one embodiment, the reconfiguration phase comprises a stopping step, in which the excitation unit at least temporarily stops the implementation of the excitation phase; a new excitation phase being implemented at the end of the reconfiguration phase.

[0062] Stopping the excitation phase allows the magnetic component to return to the initial magnetic configuration before implementing the excitation phase again.

[0063] According to one embodiment, a new initialization phase is implemented at the end of the reconfiguration phase.

[0064] Thus, it is possible to place the magnetic component in the initial magnetic configuration, even when the downstream chamber is entirely in the second magnetic state. It is also possible to actively replace the magnetic component in the initial magnetic configuration to save time.

[0065] According to one embodiment, the reconfiguration phase further comprises a modification step implemented after the detection step, in which the reconfiguration unit modifies the magnetic transmission value of the junction member.

[0066] In this way, it is possible to artificially reproduce a succession of chambers separated by junction members having a magnetic transmission value which varies.

[0067] The aim of the invention can also be achieved by implementing a classification method for classifying an input signal into a signal class, the classification method being implemented by a classification system as described previously and comprising the following steps: - a pre-processing step in which the pre-processing device transforms the input signal into at least one initial signal; - at least one conversion step in which a conversion method as described previously is applied by the conversion device to an initial signal among said at least one initial signal, so as to obtain a data set corresponding to said initial signal to which the conversion method is applied; - an identification step in which the identification unit associates the input signal with a signal class based on the data set obtained during the at least one conversion step

[0068] The arrangements described above make it possible to propose a method for classifying an input signal into a signal class by means of a compact conversion device.

[0069] According to one embodiment, the pre-processing step may comprise transforming the input signal into a plurality of initial signals. Each initial signal of the plurality of initial signals may be identical to or different from another of the initial signals. Thus, during each conversion step, each conversion device applies the conversion method to the initial signal associated with it.

[0070] In this way, it is possible to pre-process the input signal differently during the pre-processing step, depending on the characteristics that one wishes to extract from the input signal, or depending on the conversion device that will apply the conversion method to the initial signal thus pre-processed.

[0071] Brief description of the drawings

[0072] Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the appended drawings in which:

[0073] [Fig-1] [Fig.l] is a schematic view of a classification system according to a particular embodiment of the invention.

[0074] [Fig.2] [Fig.2] is a schematic view showing different means of implementing implements a nucleation step, via a nucleation organ.

[0075] [Fig.3] [Fig.3] is a schematic view of a conversion device according to a particular embodiment of the invention implementing certain steps of the conversion method.

[0076] [Fig.4] [Fig.4] is a schematic perspective view of a device for conversion according to a particular embodiment of the invention, and more particularly presenting the detection unit.

[0077] [Fig.5] [Fig.5] is a graph representing the evolution of the physical parameter associated with a state of deformation of the domain wall, as a function of time.

[0078] [Fig.6] [Fig.6] is a schematic side view and top view of a conversion device according to a particular embodiment of the invention comprising a fixed junction member.

[0079] [Fig.7] [Fig.7] is a schematic side view and top view of a conversion device according to a particular embodiment of the invention comprising a reconfigurable junction member.

[0080] [Fig.8] [Fig.8] is a schematic view showing different means of implementing implements a modification step, via a reconfiguration unit.

[0081] [Fig.9] [Fig.9] is a schematic view showing different means of implementing implements a modification step, via a reconfiguration unit.

[0082] [Fig. 10] [Fig. 10] is a schematic view showing certain steps of the initialization phase.

[0083] [Fig. 11] [Fig. 11] is a schematic view of a classification method according to a particular embodiment of the invention.

[0084] [Fig. 12] [Fig.l] is a schematic view of a classification method according to a particular embodiment of the invention. Detailed description

[0085] In the figures and in the remainder of the description, the same references represent identical or similar elements. In addition, the different elements are not shown to scale so as to enhance the clarity of the figures. Furthermore, the different embodiments and variants are not mutually exclusive and can be combined with each other.

[0086] As illustrated in Figures 1 to 9, the invention relates to a conversion device 10 for converting an initial signal denoted “SI” into a data set denoted “SC”. For example, the initial signal SI may correspond to an input signal denoted “SE” having been pre-processed by a pre-processing device 3, which will be described later. The input signal SE may correspond to information to be processed, which is pre-processed into an initial signal SI that can be converted by the conversion device 10. For example, and without this being limiting, it is possible for the input signal SE to be pre-processed in the form of a succession of pulses as described in European patent application No. 22315278.6 filed in November 2022. It is also possible for the initial signal SI to correspond to a variation in amplitude, frequency, time response, or any other type of signal to excite a magnetic material.

[0087] The conversion device firstly comprises a magnetic component 20 which comprises a magnetic material configured to vary locally between a first magnetic state denoted “M1” having a first magnetization, and a second magnetic state denoted “M2” having a second magnetization different from the first magnetization. As can be seen in [Fig.l], the conversion device 10 may comprise a peripheral delimitation 11 with a closed contour in which the magnetic component 20 is fully contained. Thus, and as will be presented later, it is possible to limit the expansion of a magnetic domain wall P when it encounters the peripheral delimitation 11.Generally, the peripheral delimitation 11 is a non-magnetic zone, for example a groove dug by etching in the material constituting the magnetic component 20, a zone having undergone irradiation by a laser beam, or ion irradiation making it possible to form said non-magnetic zone. It is also possible, but not limiting, for such a peripheral delimitation 11 to be quadrilateral. Thus, the manufacture of the conversion device 10 is simplified.

[0088] The magnetic component 20 is subdivided into a plurality of zones, where each zone is either in the first magnetic state M1 or in the second magnetic state M2. Each zone in the first magnetic state M1 is separated from a zone in the second magnetic state M2 by a magnetic domain wall P. By "magnetic domain wall P" is meant a boundary separating two zones of the same continuous magnetic medium which are not in the same magnetic state. Generally, the magnetic material of the magnetic component 20 is inhomogeneous. In other words, in most configurations, the magnetic component 20 comprises a plurality of zones, where at least one zone of the plurality of zones is in the first magnetic state M1, and where at least one other zone of the plurality of zones is in the second magnetic state M2.

[0089] The conversion device 10 also comprises a junction member 30 separating the magnetic component 20 between an upstream chamber 21 and a downstream chamber 23. [Fig.l] represents in particular an embodiment in which the upstream chamber 21 is entirely in the second magnetic state M2, and in which the downstream chamber 23 is entirely in the first magnetic state ML. The junction member ensures magnetic communication between the upstream chamber 21 and the downstream chamber 23, said junction member 30 being characterized by a magnetic transmission value noted “Rtr” corresponding to a capacity of the junction member 30 to allow a displacement of the magnetic domain wall P in a propagation direction noted “X”, said propagation direction X being defined from the upstream chamber 21 to the downstream chamber 23. By "magnetic transmission value Rtr" is meant the capacity of the junction member 30 to allow the transmission of a wall of magnetic domain P. In other words, this "magnetic transmission value Rtr" corresponds to the inverse of a resistance that the junction member 30 can produce on the passage of a wall of magnetic domain P. Generally speaking, the propagation of the wall of magnetic domain P within one of the two chambers 21, 23 is easier than its propagation through the junction member 30. The junction member 30 therefore acts as a door constituting a brake on the propagation of the wall of magnetic domain P between the upstream chamber 21 and the downstream chamber 23.

[0090] The conversion device 10 also comprises an initialization unit 40 configured to place the magnetic component 20 in an initial magnetic configuration denoted “Cl”, in which the magnetic domain wall P is arranged at the level of the junction member 30. Such an initial magnetic configuration Cl is for example represented in [Fig. 1].

[0091] According to one embodiment, the conversion device 10 comprises a nucleation member 41 configured to place the magnetic component 20 in a magnetic nucleation configuration denoted C0, in which all the zones of the magnetic component 20 are placed in the first magnetic state M1, with the exception of a nucleation zone which is placed in the second magnetic state M2, said nucleation zone being contained in the upstream chamber 21. It is moreover possible for the initialization unit 40 to comprise the nucleation member 4L. [Fig. 2] presents different variants of nucleation members 4L. The placement of the magnetic component 20 in the magnetic nucleation configuration C0 is particularly useful in the case where the entire conversion device 10 is in the first magnetic state ML. In this case, the nucleation member 41 makes it possible to form a zone in the second magnetic state M2, and thus create a magnetic domain wall. P.

[0092] [Fig.2] A shows a nucleation member 41 configured to apply a local magnetic field, to form the nucleation zone. Generally, a nucleation member 41 may comprise a device of the electromagnet or permanent magnet type for applying a local magnetic field. [Fig.2] B shows a nucleation member 41 configured to apply a local magnetic field, which is associated with the presence of an intrinsic defect 42 in the magnetic material, or created deliberately. The creation of a defect 42 in the upstream chamber 21 thus serves as a privileged center to facilitate nucleation. This defect 42 may in particular be created by a local modification of the properties of the magnetic layer by different means such as: a laser beam, an FIB beam (for Focused Ion Beam according to the dedicated Anglo-Saxon terminology) or even an optical or electronic lithography step followed by an etching step. [Fig. 2] C shows a nucleation member 41 configured to apply a local magnetic field when it is associated with the presence of a magnetic layer 44 added to the magnetic component 20. A non-magnetic layer 46 may also be interposed or not between the magnetic component 20 and the magnetic layer 44. This magnetic layer 44, or this stack of layers 44, 46 may in particular have a planar magnetic anisotropy. [Fig. 2] D shows a nucleation member 41 configured to apply a local or global magnetic field associated with local heating. The nucleation member 41 may then comprise a local heating device 47 configured to generate such local heating by means of an electric current, a localized laser beam, or any other means. [Fig.2] E shows a nucleation member 41 configured to apply a local magnetic field in the presence of a local electric field. In this case, the electric field can be used to lower the magnetic anisotropy barrier. Finally, [Fig.2] F shows a nucleation member 41 configured to inject a spin-polarized current, for example by defining on the upstream chamber 21 a pillar of a magnetic stack of the magnetic tunnel junction or spin valve type. The current is then injected as shown [Fig.2] F. It is understood that these different embodiments of the nucleation member 41 are not limiting.

[0093] According to one embodiment, the initialization unit 40 comprises an expansion member 43 configured to move the magnetic domain wall P to the junction member 30, so as to place the magnetic component 20 in the initial magnetic configuration CL. Thus, it is possible to place the conversion device 10 in a configuration in which a physical excitation generated by the excitation unit 50, described below, only contributes to moving the magnetic domain wall P beyond the junction member 30 in the downstream chamber 23. According to a first variant, the expansion member 43 is configured to move the magnetic domain wall P in the propagation direction X, for example once the nucleation member 41 has formed a nucleation zone.According to another variant, it is possible for the expansion member 43 to be configured to move the magnetic domain wall P in a direction opposite to the propagation direction X, for example to return the magnetic domain wall P to the level of the junction member 30 when it has moved inside the downstream chamber 23. The arrangements previously described therefore allow the expansion member 43 to replace the magnetic component 20 in the initial magnetic configuration CL.

[0094] Different variants can be used to implement the expansion member 43. According to a first variant, the expansion member 43 comprises a magnetic field generator, such as an electromagnet or permanent magnet type device for applying a local magnetic field. According to a second variant, the expansion member 43 comprises a spin-polarized current generator. It is also possible for the expansion member 43 to comprise the nucleation member 41.

[0095] The conversion device 10 further comprises an excitation unit 50 configured to generate a physical excitation in order to excite the magnetic material, so as to move the magnetic domain wall P in the propagation direction X, the physical excitation being generated as a function of the initial signal SI. For example, the physical excitation corresponds to a signal comprising electric current pulses or magnetic field pulses. For this, the excitation unit 50 may comprise a current generator 51 configured to generate an electric current, or a magnetic field generator.

[0096] According to one embodiment, the initialization unit 40 comprises the excitation unit 50, the excitation unit 50 then being configured to move the magnetic domain wall P to the junction member 30, so as to place the magnetic component 20 in the initial magnetic configuration C1. In other words, the excitation unit 50 comprises the expansion member 43.

[0097] According to one embodiment, the excitation unit 50 can be configured to place the magnetic component 20 in the initial magnetic configuration C1 in the case where the magnetic domain wall P has passed the junction member 30 and is placed in the downstream chamber 23.

[0098] Synergistically, the use of a current generator 51 as an excitation unit 50 in a conversion device 10 comprising only two chambers 21, 23 makes it possible to reduce the energy consumption of the system while maintaining good conversion quality of the initial signal SI by the conversion device 10. Furthermore, the current generator 51 can act both as an expansion member 43 and as an excitation unit 50. [Fig. 3] illustrates the conversion device 10 according to different configurations. [Fig. 3] A shows the conversion device 10 when the magnetic component 20 is in the nucleation configuration C0. [Fig. 3] B shows the conversion device 10 when the magnetic component 20 is in the initial configuration CL. The current generator 51 can be configured to: - inject an electric current to move the magnetic domain wall P in the propagation direction X to cause the magnetic component 20 to pass from the nucleation magnetic configuration C0 to the initial magnetic configuration Cl; - inject an electric current to move the magnetic domain wall P in the direction of propagation X beyond the junction member 30; - inject a reverse electric current, to move the magnetic domain wall P in a direction opposite to the propagation direction X, to return the magnetic domain wall P at the level of the junction member 30, to the initial magnetic configuration Cl.

[0099] Thus, the three functions are fulfilled by a single element.

[0100] The conversion device 10 further comprises a detection unit 60 arranged at the downstream chamber 23. The detection unit 60 is configured to detect and record at least one characteristic triggering parameter denoted “Nbf” at the moment when a physical parameter associated with a deformation state of the magnetic domain wall P exceeds a predetermined threshold value denoted “Vs”. Different variants can be used for the implementation of the detection unit 60. According to a first variant, the detection unit 60 comprises an optical detector such as a Kerr effect optical microscope, wide field or focused. [Fig.4] illustrates a second variant in which the detection unit 60 operates by electrical detection.In this case, the detection unit 60 can electrically detect the at least one trigger parameter by means of a magnetic tunnel junction (tunnel magnetoresistance signal), or a spin valve (giant magnetoresistance signal). More precisely, the detection unit 60 can comprise a pillar 61 arranged on the magnetic component 20 vertically above the downstream chamber 23. It is not necessary for this pillar 61 to be centered on the downstream chamber 23. Indeed, and advantageously, the position of the pillar 61 relative to the junction member 30 makes it possible to contribute to setting the predetermined threshold value VS. According to one embodiment, the pillar 61 can comprise a spin valve type or magnetic tunnel junction type stack comprising: . - a contact electrode 62 for reading the electrical signal; - a layer 63 of an insulating material (for example MgO, AIOx, HfO2, ... in the context of a magnetic tunnel junction stack), or of a non-ferromagnetic electrically conductive material in the case of a spin valve type stack; - a layer of a magnetic stack 64 constituting the reference magnetic electrode.

[0101] According to a first variant, the contact electrode 62 is a magnetic layer magnetically coupled to the magnetic material constituting the magnetic component 20, the local magnetic state then being read at the level of the spin valve type stack or the magnetic tunnel junction type stack. Alternatively, it is possible to omit the magnetic layer 62. The layer 63 of an insulating material, in the case of a magnetic tunnel junction, or the layer 63 of a conductive material non-ferromagnetic electrical energy in the case of a spin valve type stack, is deposited directly on the magnetic material constituting the magnetic component 20. The local magnetic state is then read at the level of the spin valve type stack or the magnetic tunnel junction type stack

[0102] The detection unit 60 may also comprise an electrical device for reading the resistance of the pillar 61, as well as contacts which are not shown in [Fig.4].

[0103] According to one embodiment, the physical parameter associated with a state of deformation of the magnetic domain wall P is a distance denoted “d” counted in the propagation direction X from the junction member 30, the characteristic triggering parameter Nbf being detected and recorded by the detection unit 60 at the moment when this distance d exceeds a predetermined threshold distance VS. Figures 3 CF illustrate the conversion device 10 when the magnetic domain wall P moves in the downstream chamber 23. According to one possibility, the predetermined threshold value VS is a fixed distance counted between the junction member 20 and a position in the downstream chamber 23, as illustrated in Figures 3 C and D. In this case, a triggering parameter Nbf may be detected when the magnetic domain wall P exceeds this fixed distance VS, as illustrated in [Fig. 3] D. This fixed distance VS not being crossed in [Fig.3] C, a characteristic trigger parameter Nbf is therefore not detected.

[0104] Alternatively, the physical parameter associated with a deformation state of the magnetic domain wall P may be a measurement of area or of an area ratio, the trigger characteristic parameter Nbf may then be detected and recorded by the detection unit 60 at the moment when this area or this area ratio exceeds the predetermined threshold value VS. For example, the predetermined threshold value VS may correspond to a maximum area Amax of the downstream chamber 23, and the physical parameter may correspond to Do A of the area of ​​the downstream chamber 23 which is in the second magnetic state M2, as shown in [Fig. 3] D. In this case, a trigger characteristic parameter Nbf may then be detected when the entire downstream chamber 23 is in the second magnetic state M2, i.e. when A=Amax, or when the ratio A / Amax=1, as shown in [Fig. 3] E.

[0105] [Fig.5] is a graph which represents the variation of a physical parameter of the magnetic component 20, associated with a state of deformation of the domain wall in the downstream chamber 23, as a function of the current pulses generated by the physical excitation of the excitation unit 50.

[0106] Whatever the variant considered, the data set SC comprises said at least one characteristic triggering parameter Nbf. For example, the set of SC data is a number corresponding to the number of times a trigger characteristic parameter Nbf is recorded by the detection unit 60. In other words, the SC data set is equal to the sum of the detected trigger characteristic parameters Nbf.

[0107] Generally, the detection unit 60 may comprise a memory configured to record the SC data set.

[0108] According to a non-limiting variant, the excitation unit 50 can be configured to at least temporarily stop the physical excitation of the magnetic material when the following condition is verified: at least one characteristic triggering parameter Nbf is detected by the detection unit 60. However, it is generally provided that the physical excitation is only stopped by the excitation unit 50 at the temporal end of the initial signal SI.

[0109] Advantageously, the initialization unit 40 can be configured to place the magnetic component 20 in the initial magnetic configuration C1 when the following condition is satisfied: the at least one characteristic triggering parameter Nbf is detected by the detection unit 60. The fact of being able to reset the magnetic component 20 by placing it in the initial magnetic configuration C1 after each detection of a characteristic triggering parameter Nbf makes it possible to accelerate the return of the magnetic component 20 to the initial magnetic configuration C1, which makes it possible to temporally detect a maximum of characteristic triggering parameters Nbf by the conversion device 10. [Fig. 3] F illustrates the conversion device 10 in a configuration where the initialization unit 40 is in the process of replacing the magnetic component 20 in the initial magnetic configuration C1.

[0110] Although the magnetic transmission value Rtr of the junction member 30 may be fixed (as shown in [Fig.6]), it is also possible to modify this magnetic transmission value Rtr (as shown in [Fig.7]). In this case, and as illustrated in [Fig.7], the conversion device 10 may comprise a reconfiguration unit 70 configured to modify the magnetic transmission value Rtr of the junction member 30. This makes it possible to adapt the junction member 30 to the initial signal SI to be converted. For example, the reconfiguration unit 70 may be configured to modify the magnetic transmission value Rtr of the junction member 30 each time the detection unit 60 detects a trigger characteristic parameter Nbf.Thus, it is possible to modify the magnetic transmission value Rtr of the junction member 30 at the time of placement of the magnetic component 20 in the initial magnetic configuration CL. This makes it possible to artificially reproduce a succession of chambers separated by junction members 30 having a magnetic transmission value Rtr which varies. In other words, the junction member 30 is reconfigurable. There are different variants for reconfiguring junction members 30. Generally, the production of junction members 30 or their reconfiguration is implemented by controlling and modifying the local magnetic properties of the magnetic material constituting the magnetic component 20. The different variants proposed below are different embodiments allowing those skilled in the art to implement reconfiguration units, and are not limiting.

[0111] [Fig.8] AB represents a reconfiguration unit 70 capable of modifying the magnetic transmission value Rtr of the junction member 30 by applying a local magnetic field. [Fig.8] A represents more particularly a reconfiguration unit 70 configured to apply a local magnetic field by means of a magnetic element 71 whose magnetization is perpendicular to the plane. This magnetic element 71 can be separated from the junction member 30 by a non-magnetic element 73. [Fig.8] B represents a reconfiguration unit 70 configured to apply a local magnetic field by means of a magnetic element 75 whose magnetization is in the plane. This magnetic element 75 can be separated from the junction member 30 by a non-magnetic element 73. Other variants not shown such as the use of a spin valve or magnetic tunnel junction type structure can also be used to obtain a reconfiguration unit 70.

[0112] Those skilled in the art may, for example, refer to European patent application number 23315104.2 filed on April 25, 2023 to obtain a reconfiguration unit 70.

[0113] [Fig.9] A represents a reconfiguration unit 70 capable of modifying the magnetic transmission value Rtr of the junction member 30 by means of a local electric field produced for example by the application of an electric voltage V. More particularly, the local electric field makes it possible to modulate the magnetic properties of a magnetic layer and in particular its anisotropy and the Dzyaloshinskii Moryia interaction. [Fig.9] A presents in particular a conductive electrode 72 on which a voltage V is applied by means of a voltage generator 74. According to this embodiment, it is possible for a dielectric layer 76 to be interposed between the conductive electrode 72 and the junction member 30.

[0114] Figures 9 B and C show a reconfiguration unit 70 capable of modifying the magnetic transmission value Rtr of the junction member 30 by means of local heating. More precisely, [Fig.9] B shows a conductive layer 77a into which an electric current denoted “I” is injected by means of a current generator 77b in order to raise the temperature of the conductive layer 77a by Joule effect. The generated temperature is thus transmitted to the junction member 30 directly, or by means of an intermediate layer 78 arranged between the junction member and the conductive layer 77a. This intermediate layer 78 may for example be a layer made of a dielectric material, so as to electrically insulate the junction member 30 from the conductive layer 77a into which the current is injected. Local heating may also be carried out by means of a hot tip, for example an atomic force microscopy tip or AFM (for Atomic Force Microscopy according to the established English terminology) brought close to the junction member or by means of a laser 77c focused locally as shown in [Fig.9] C. For this, it is possible to have an absorption layer 77d configured to absorb the energy received from the laser 77c.

[0115] All of the arrangements previously described make it possible to propose a conversion device 10 capable of converting an initial signal SI into a set of data SC comprising one or more characteristic triggering parameters Nbf. This type of device is particularly suitable for applications of the artificial neuron type. Furthermore, the use of only two chambers 21, 23 makes it possible to obtain a more compact conversion device 10 requiring a lower electrical energy input.

[0116] As indicated previously, the invention also relates to a classification system 1 intended to classify an input signal SE into a signal class denoted “Ci”. An example of such a classification system 1 is shown in [Fig.l].

[0117] Classification system 1 includes: - at least one pre-processing device 3 intended to transform the input signal SE into an initial signal SI; - at least one conversion device 10 as described previously taking as input said initial signal SI and converting the initial signal SI into a set of data SC; - an identification unit 5 taking as input the data set SC and configured to associate the input signal SE with a signal class Ci as a function of the data set SC, said signal class Ci being chosen from a set of predetermined signal classes recorded in a memory 7 of the classification system 1.

[0118] The arrangements described above make it possible to propose a classification system 1 capable of classifying an input signal SE as a function of the response detected by the conversion device 10.

[0119] According to a variant not shown, it is possible for the classification system 1 to comprise at least two conversion devices 10. These different conversion devices 10 may have the same initial signal SI as input. Alternatively, the conversion devices 10 may have a distinct and different signal SI as input for each of the conversion devices 10, said initial signal SI being obtained in transforming the same input signal SE by means of a separate pre-processing device 3 associated with each of the conversion devices 10. In this way, it is possible to improve the classification quality of the input signal SE into a data set SC. It is furthermore possible to carry out at least two conversions of the initial signal SI into a data set SC, to improve the signal conversion.

[0120] According to a first possibility, the classification system 1 may comprise a pre-processing device 3 capable of converting the input signal SE into a plurality of initial signals SI, which may or may not be distinct. Each initial signal SI of the plurality of initial signals SI is then associated with one of the conversion devices 10. Thus, it is possible to obtain different sets of data SC from each of the conversion devices 10. According to a second possibility, the classification system 1 may comprise several pre-processing devices 3, each intended to convert the input signal SE into an initial signal SI. It is therefore clearly understood that for each of the conversion devices 10, it is possible to obtain different initial signals SI, from a single input signal SE.

[0121] The invention also relates to a method for converting an initial signal SI into a set of data SC. Generally, the initial signal SI and the physical excitation are a function of time. In this case, it may be provided that the conversion method is stopped at the time end of the physical excitation. This conversion method is implemented by a conversion device 10 as described previously. Figures 3 and 10 to 12 show different phases and steps of the conversion method.

[0122] The conversion method comprises a PL initialization phase

[0123] According to one embodiment, the initialization unit 40 of the conversion device 10 may comprise a nucleation member 4L. In this case, it is possible for the initialization phase PI to comprise a nucleation step E1, in which the nucleation member 41 places the magnetic component 20 in the magnetic nucleation configuration C0 in which all the zones of the magnetic component 20 are placed in the first magnetic state M1, with the exception of a nucleation zone which is placed in the second magnetic state M2, said nucleation zone being contained in the upstream chamber 21. Thus, it is possible to prepare the conversion device 10 to carry out a conversion, in particular when it has not been used for a long time.

[0124] The initialization phase PI also comprises an initial step E13 in which the magnetic component 20 is placed in the initial magnetic configuration CL. In the case where a nucleation step Eli is implemented, the initialization unit 40 can for example be configured to place the magnetic component 20 in the initial magnetic configuration Cl, for example via the member expansion 43. For example, the initial magnetic configuration Cl corresponds to a configuration where the inhomogeneous magnetic material is in the second magnetic state M2 in the upstream chamber 21, and in the first magnetic state Ml in the downstream chamber 23, or vice versa.

[0125] The conversion method also comprises an excitation phase P2 in which the excitation unit 50 generates the physical excitation as a function of the initial signal SI, so as to move the magnetic domain wall P. As illustrated in [Fig.10], the initial step E13 can be implemented at the same time as the excitation phase P2. In other words, it is the physical excitation generated during the excitation phase P2 which makes it possible to move the magnetic domain wall P towards the junction member 30 so as to pass from the magnetic nucleation configuration CO to the initial magnetic configuration C1.

[0126] The conversion method also comprises a reconfiguration phase P3 implemented if the detection unit 60 detects that the at least one physical parameter associated with the deformation state of the magnetic domain wall P exceeds the predetermined threshold value Vs. The reconfiguration phase P3 then comprises a detection step E31 in which the detection unit 60 records at least one characteristic triggering parameter Nbf in the data set SC. It is therefore well understood that the excitation phase P2 is implemented continuously, and that several detection steps E31 can be implemented, in particular each time that the at least one physical parameter associated with the deformation state of the magnetic domain wall P exceeds the predetermined threshold value Vs.According to a first variant, the detection step can be implemented when the magnetic material present in the downstream chamber 23 is entirely in the second magnetic state M2. Thus, the detection of the exceeding of the predetermined threshold value Vs by the physical parameter associated with the deformation of the magnetic wall is simpler. However, such a variant is not limiting, and it is also possible for the detection step E31 to be implemented when the magnetic domain wall P crosses a threshold distance Vs as shown in [Fig.3] D. .

[0127] According to a variant not shown, the reconfiguration phase P3 may comprise a stopping step E32, in which the excitation unit 50 at least temporarily stops the implementation of the excitation phase P2; a new excitation phase P2 being implemented at the end of the reconfiguration phase P3. Stopping the excitation phase P2 allows the magnetic component 20 to return to the initial magnetic configuration C1 before implementing the excitation phase P2 again.

[0128] Each time a characteristic triggering parameter is detected during the detection step E31, it is advantageous to implement a new phase initialization step PI at the end of the reconfiguration phase P3. More particularly, once a detection step E31 is implemented, the initialization unit 40 can replace the magnetic component 20 in the initial magnetic configuration C1 by implementing a new initial step E13. It is therefore clearly understood that according to this embodiment, a new initial step is implemented each time a detection step is implemented. As has been specified with reference to the conversion device, the initial step E13 can be implemented by the excitation unit 50 when the initialization unit 40 comprises the excitation unit 50.In the particular case where the excitation unit 50 comprises a current generator 51, it is advantageous for the initial steps E13 implemented after the detection steps E31 to be carried out by injecting an electric current by the current generator 51 in a direction opposite to the propagation direction X. It is thus possible to actively replace the magnetic component 20 in the initial magnetic configuration C1 to save time. It is also well understood that the implementation of a nucleation step E13 is independent of the implementation of an initial step E11. For example, the conversion method may comprise a single nucleation step E11, and a plurality of initial steps E13 implemented (actively or not), after each detection step E31.

[0129] According to a non-limiting variant in which the conversion device 10 comprises a reconfiguration unit, the reconfiguration phase P3 may also comprise a modification step E33 implemented after the detection step E31, in which the reconfiguration unit 70 modifies the magnetic transmission value Rtr of the junction member 30. In this way, it is possible to artificially reproduce a succession of chambers separated by junction members having a magnetic transmission value Rtr which varies. Such a variant is for example represented in [Fig. 12].

[0130] The arrangements described above make it possible to propose a conversion method making it possible to convert an initial signal SI into a set of data SC by a conversion device 10 which can use only two chambers of a magnetic material.

[0131] Finally, and as illustrated in Figures 11 and 12, the invention relates to a classification method for classifying an input signal SE into a signal class Ci. The classification method is implemented by a classification system 1 as described previously and comprises the following steps: - a pre-processing step E0 in which the pre-processing device 3 transforms the input signal SE into an initial signal SI; - at least one conversion step E1 in which a conversion method as described previously is applied by the conversion device 10 to the initial signal SI, so as to obtain a set of data SC corresponding to the initial signal SI; - an identification step E2 in which the identification unit 5 associates the input signal SE with a signal class Ci as a function of the data set SC obtained during the at least one conversion step El

[0132] The arrangements described above make it possible to propose a method for classifying an input signal SE into a signal class by means of a compact conversion device 10. The classification method can therefore comprise one or more conversion steps E1, depending on the number of conversion devices 10 in particular.

[0133] According to a variant not shown, in which the classification system 1 comprises N (N being an integer greater than or equal to 2) conversion devices 10, it is possible that the preprocessing step E0 comprises the transformation of the input signal SE into N initial signals SI. For example, these initial signals SI may be different or identical. These initial signals SI may each be associated with one of the N conversion devices 10.

[0134] Thus, it is possible to adapt the pre-processing step E0 to obtain an initial signal either as a function of the conversion device 10 with which it is associated, or as a function of a particular characteristic that one wishes to extract, or both. For example, it is possible to implement the pre-processing step as a function of the magnetic transmission values ​​Rtr of each of the junction members 30 of the N conversion devices 10.

[0135] According to this variant, the classification method can comprise N conversion steps E1, implemented by the N conversion devices 10, and the conversion method will make it possible to obtain N sets of data SC. The identification step E2 can then consist of associating a signal class with the input signal SE, as a function of the N sets of data SC obtained during the N conversion steps E1.

Claims

Claims

1. Conversion device (10) for converting an initial signal (SI) into a data set (SC), the conversion device (10) comprising: a magnetic component (20) comprising a magnetic material configured to vary locally between a first magnetic state (Ml) having a first magnetization, and a second magnetic state (M2) having a second magnetization different from the first magnetization, said magnetic component (20) being subdivided into a plurality of zones, where each zone is either in the first magnetic state (Ml) or in the second magnetic state (M2); each zone in the first magnetic state (Ml) being separated from a zone in the second magnetic state (M2) by a magnetic domain wall (P); a junction member (30) separating the magnetic component (20) between an upstream chamber (21) and a downstream chamber (23) and ensuring magnetic communication between the upstream chamber (21) and the downstream chamber (23), said junction member (30) being characterized by a magnetic transmission value (Rtr) corresponding to a capacity of the junction member (30) to allow a displacement of the magnetic domain wall (P) in a propagation direction (X), said propagation direction (X) being defined from the upstream chamber (21) towards the downstream chamber (23); an initialization unit (40) configured to place the magnetic component (20) in an initial magnetic configuration (Cl), in which the magnetic domain wall (P) is arranged at the junction member (30); an excitation unit (50) configured to generate a physical excitation in order to excite the magnetic material, so as to move the magnetic domain wall (P) in the propagation direction (X), the physical excitation being generated according to the initial signal (SI); a detection unit (60) arranged at the downstream chamber (23), said detection unit (60) being configured to detect and record at least one characteristic parameter trigger (Nbf) at the moment when a physical parameter associated with a deformation state of the magnetic domain wall (P) exceeds a predetermined threshold value (Vs), the data set (SC) comprising said at least one characteristic trigger parameter (Nbf).

2. A conversion device (10) according to claim 1, further comprising a closed-contour peripheral boundary (11) in which the magnetic component (20) is fully contained.

3. Conversion device (10) according to any one of claims 1 or 2, wherein the initialization unit (40) is configured to place the magnetic component (20) in the initial magnetic configuration (Cl) when the following condition is verified: the at least one trigger characteristic parameter (Nbf) is detected by the detection unit (60).

4. Conversion device (10) according to any one of claims 1 to 3, wherein the initialization unit (40) comprises an expansion member (43) configured to move the magnetic domain wall (P) to the junction member (30), so as to place the magnetic component (20) in the initial magnetic configuration (Cl).

5. Conversion device (10) according to any one of claims 1 to 4, further comprising a reconfiguration unit (70) configured to modify the magnetic transmission value (Rtr) of the junction member (30).

6. A conversion device (10) according to any one of claims 1 to 5, wherein the excitation unit (50) comprises a current generator (51) configured to generate an electric current.

7. Classification system (1) for classifying an input signal (SE) into a signal class (Ci), the classification system (1) comprising: • at least one pre-processing device (3) for transforming the input signal (SE) into at least one initial signal (SI); • at least one conversion device (10) according to any one of claims 1 to 6 taking as input an initial signal (SI) from said at least one initial signal (SI) and converting said initial signal (SI) taken as input, into a data set (SC); • an identification unit (5) taking as input the data set (SC) and configured to associate the input signal (SE) with a signal class (Ci) as a function of the data set (SC), said signal class (Ci) being chosen from a set of predetermined signal classes recorded in a memory (7) of the classification system (1).

8. A method of converting an initial signal (SI) into a data set (SC), the conversion method being implemented by a conversion device (10) according to any one of claims 1 to 6, and comprising the following phases: • an initialization phase (PI) comprising an initial step (El3) in which the magnetic component (20) is placed in the initial magnetic configuration (Cl); • an excitation phase (P2) in which the excitation unit (50) generates the physical excitation as a function of the initial signal (SI), so as to move the magnetic domain wall (P); • a reconfiguration phase (P3) implemented if the detection unit (60) detects that the at least one physical parameter associated with the deformation state of the magnetic domain wall (P) exceeds the predetermined threshold value (Vs), the reconfiguration phase (P3) then comprising a detection step (E31) in which the detection unit (60) records at least one characteristic triggering parameter (Nbf) in the data set (SC).

9. Conversion method according to claim 8, in which the initialization unit (40) comprises a nucleation member (41), the initialization phase (PI) then comprising a nucleation step (Eli), implemented before the initial step (E13), in which the nucleation member (41) places the magnetic component (20) in the magnetic nucleation configuration (C0) in which all the zones of the magnetic component (20) are placed in the first ma- genetic (Ml), with the exception of a nucleation zone which is placed in the second magnetic state (M2), said nucleation zone being contained in the upstream chamber (21).

10. Conversion method according to any one of claims 8 or 9, wherein the reconfiguration phase (P3) comprises a stopping step (E32), in which the excitation unit (50) at least temporarily stops the implementation of the excitation phase (P2); a new excitation phase (P2) being implemented at the end of the reconfiguration phase (P3).

11. Conversion method according to any one of claims 8 to 10, in which a new initialization phase (PI) is implemented at the end of the reconfiguration phase (P3).

12. Conversion method according to any one of claims 8 to 11, implemented by a conversion device (10) according to claim 5, in which the reconfiguration phase (P3) further comprises a modification step (E33) implemented after the detection step (E31), in which the reconfiguration unit (70) modifies the magnetic transmission value (Rtr) of the junction member (30).

13. Classification method for classifying an input signal (SE) into a signal class (Ci), the classification method being implemented by a classification system (1) according to claim 7 and comprising the following steps: • a pre-processing step (E0) in which the pre-processing device (3) transforms the input signal (SE) into at least one initial signal (SI); • at least one conversion step (El) in which a conversion method according to any one of claims 8 to 12 is applied by the conversion device (10) to an initial signal (SI) among said at least one initial signal (SI), so as to obtain a data set (SC) corresponding to said initial signal (SI) to which the conversion method is applied;• an identification step (E2) in which the identification unit (5) associates the input signal (SE) with a signal class (Ci) as a function of the data set (SC) obtained during the at least one conversion step (El);

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