A solid-state functional device and system based on first-order magnetic phase transition step effect

Abstract

This invention discloses a solid-state functional device and system based on the first-order magnetic phase transition step effect, belonging to the field of energy converter technology. It solves the technical problems of large phase transition hysteresis losses and poor cycle controllability in existing solutions. The device includes a magnetic phase transition functional unit and a signal interaction unit. The magnetic phase transition functional unit is made of a material with first-order magnetic phase transition characteristics, which are manifested as a step-like abrupt change in the macroscopic magnetization intensity of the material near the phase transition point under external excitation. This invention breaks through the traditional energy pumping approach that relies on continuous changes in physical properties and external parameter resonance, achieving high instantaneous power density power output, ultra-high sensitivity physical quantity sensing, or precision micro-actuation. The achievable magnetic flux change rate is orders of magnitude higher than traditional solutions, thereby greatly improving the instantaneous power density and sensing response sensitivity of the system.

Description

Technical Field

[0001] This invention relates to the field of energy converter technology, specifically to a solid-state functional device and system based on the first-order magnetic phase transition step effect. Background Technology

[0002] Current conversion and sensing technologies are mainly based on the continuous changes in the physical properties of materials. Traditional power generation technologies are mainly based on two principles: one is the rotary generator based on Faraday's law of electromagnetic induction. This type of technology relies on continuous macroscopic mechanical motion, which brings inherent defects such as mechanical wear, high noise, and high maintenance costs; the other is thermoelectric conversion technology based on the Seebeck effect. Due to the limitations of the thermoelectric potential properties of the materials themselves, its conversion efficiency is generally low, and it is difficult to achieve a significant leap in principle.

[0003] To address static conversion requirements, some existing technologies utilize changes in the physical properties of magnetic materials. For example, one approach leverages the continuous change in permeability of magnetic materials near the Curie temperature, modulating the magnetic reluctance of the magnetic circuit by periodically altering the material temperature, and accumulating energy through the parametric resonance principle using an external LC resonant circuit. The physical essence of this approach lies in utilizing the material's second-order phase transition or continuous physical evolution process. However, its energy release rate is limited by the external excitation period, resulting in a low rate of change in magnetic flux. Such systems typically require complex resonant circuits, fluid circulation, and precision valves, making it difficult to achieve high instantaneous power density, and they do not address the intrinsic abrupt changes in the material's properties.

[0004] Furthermore, in the fields of sensing and micro-actuation, existing sensors mostly rely on continuous and weak changes in physical quantities, resulting in signal-to-noise ratio and sensitivity being limited by the linear range of material response. Micro-actuators, on the other hand, mainly rely on continuous driving principles such as piezoelectricity and electrostatics, where displacement and response speed are often mutually constrained in practical applications.

[0005] Although first-order phase transitions in magnetic materials are accompanied by dramatic, discontinuous jumps in physical quantities such as magnetization and volume, current applied research mainly focuses on magnetic refrigeration and data storage. While a few studies have explored their potential in energy conversion, none have addressed the application logic of "discontinuous jumps in magnetization" as the core conversion mechanism. A long-standing technical challenge in this field is how to break free from the dependence on continuous changes in material properties and find a physical mechanism capable of generating intrinsic, step-like magnetic flux abrupt changes, thereby fundamentally overcoming the power density and sensitivity bottlenecks of traditional static conversion technologies. Because first-order magnetic phase transitions are typically accompanied by significant thermal hysteresis, a prevailing technical bias exists in the field that first-order magnetic phase transitions suffer from high losses and poor cycle controllability, making it difficult to construct efficient energy conversion cycles. This significantly hinders the exploration of its role as the core physical basis for multifunctional devices.

[0006] Existing technical solutions suffer from high phase transition hysteresis losses and poor cycle controllability. This has led to a common technical bias in the field, which holds that primary magnetic phase change materials are unsuitable for constructing efficient and controllable solid-state energy conversion or sensing device cores due to their high hysteresis and difficulty in cycle control. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a solid-state functional device and system based on the first-order magnetic phase transition step effect, which solves the technical problems of large phase transition hysteresis loss and poor cycle controllability in existing technical solutions.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a solid-state functional device based on the first-order magnetic phase transition step effect, comprising a magnetic phase transition functional unit and a signal interaction unit. The magnetic phase transition functional unit is made of a material with first-order magnetic phase transition characteristics. The first-order magnetic phase transition characteristics are manifested as follows: under external excitation, the macroscopic magnetization of the material undergoes a step-like abrupt change near the phase transition point. The signal interaction unit is coupled to the magnetic phase change function unit through a physical field to capture the energy or signal change generated when the macroscopic magnetization intensity undergoes a step change, and convert it into an electrical, magnetic, thermal or force signal output. The signal interaction unit and the magnetic phase change function unit are coupled by non-contact magnetic coupling, non-contact thermal coupling, or mechanical contact coupling.

[0009] By utilizing the nonlinear abrupt change in magnetization at the phase transition critical point of primary magnetic phase transition materials, a high degree of integration of energy conversion is achieved. The magnetic phase transition functional unit, as the core of energy conversion, amplifies minute external environmental excitations into significant magnetic moment change signals. Through non-contact or mechanical coupling, the signal interaction unit effectively captures these sudden magnetic flux changes, converting them into directly usable electrical signals or other physical quantity signals. This avoids the low energy conversion efficiency of traditional devices during quasi-static conversion, improving signal response speed and signal-to-noise ratio. In some embodiments, the material of the magnetic phase change functional unit is selected from at least one of FeRh alloy, MnFePSi alloy, Ni-Mn Kihasler alloy or Fe-Pd magnetic shape memory alloy.

[0010] In some embodiments, the magnetic phase transition functional unit is an epitaxially grown single-crystal thin film, and its easy magnetization axis is perpendicular to the plane of the thin film. The signal interaction unit includes an induction coil or a superconducting quantum interference device associated with the magnetic phase transition functional unit through magnetic flux coupling.

[0011] In some embodiments, when the signal interaction unit includes an induction coil, the induction coil is disposed on the surface of the magnetic phase change functional unit for sensing the instantaneous change in magnetic flux caused by the step change in macroscopic magnetization intensity and generating a pulse induced electromotive force.

[0012] In some embodiments, an excitation source and a management unit are included: the excitation source is used to provide an external energy field to drive the magnetic phase change functional unit to undergo a first-order magnetic phase change, the external energy field including at least one of a thermal field, a stress field, or a magnetic field; it is understood that the specific form of the external energy field is not limited to this, the core of which is to be able to apply a physical stimulus to the magnetic phase change functional unit sufficient to induce it to undergo a first-order phase change.

[0013] The management unit is electrically connected to the signal interaction unit and is configured to condition and store pulsed electrical energy in power generation mode.

[0014] In some embodiments, the excitation source is configured to drive the magnetic phase transition functional unit to cyclically switch between bistable states on both sides of the phase transition point, and to adjust the excitation intensity in real time through a feedback control circuit to reduce phase transition hysteresis loss; the feedback control circuit extracts a portion of energy or signal from the management unit and feeds it back to the excitation source.

[0015] In some embodiments, the magnetic phase transition functional unit and the excitation source are configured as multiple, and the system further includes a state monitoring module and a timing control module. The state monitoring module is used to monitor the magnetic state of each magnetic phase transition functional unit in real time; the timing control module is used to output time-division trigger signals to each excitation source according to the magnetic state and a preset strategy.

[0016] Beneficial Effects: This invention breaks through the traditional approach of energy pumping, which relies on continuous changes in physical properties and resonance of external parameters, and achieves high instantaneous power density output, ultra-high sensitivity physical quantity sensing, or precision micro-actuation. Because the magnetization intensity changes abruptly, shifting from the continuous, slow change of traditional schemes to a step-like abrupt change, based on the fundamental principles of electromagnetic induction, this device can theoretically achieve a much higher instantaneous magnetic flux change rate than traditional schemes, thus providing a foundation for achieving higher instantaneous power density and sensing sensitivity. By configuring different signal interaction units, the same core structure can be used to develop solutions with various functions, such as pulse power supplies, ultra-high sensitivity sensors, and fast micro-actuators. By introducing an energy management unit and forming a feedback control loop, this invention provides a clear and feasible technical path for achieving energy-sustainable or auxiliary operation of the system, improving the overall practicality of the system. Attached Figure Description

[0017] Figure 1This is a schematic diagram of a basic embodiment of the solid-state functional device and system based on the first-order magnetic phase transition step effect described in this invention, applied in power generation.

[0018] Figure 2 This is a schematic diagram of a solid-state functional device and system with an energy self-sustaining circuit based on the first-order magnetic phase transition step effect described in this invention.

[0019] Figure 3 This is a schematic diagram of the magnetization intensity of the magnetic phase change functional unit of a solid-state functional device and system based on the first-order magnetic phase change step effect described in this invention, as a function of temperature.

[0020] Figure 4 This is a schematic diagram of the timing waveforms of magnetization state, magnetic flux and induced electromotive force of a solid-state functional device and system based on the first-order magnetic phase transition step effect described in this invention during one working cycle. Detailed Implementation

[0021] The following embodiments are further exemplary descriptions of the technical solutions of the present invention, so as to enable those skilled in the art to better understand how to implement the present invention, rather than limiting the scope of protection of the present invention. Those skilled in the art should understand that, based on the core concept of utilizing the first-order magnetic phase transition step effect disclosed in the present invention, combined with the known properties of related materials (e.g., the abrupt change in magnetization intensity near the phase transition point of FeRh alloy) and fundamental physical laws (e.g., Faraday's law of electromagnetic induction), it can be implemented by adjusting specific materials, structures and parameters, and the corresponding technical effects can be expected to be obtained.

[0022] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Detailed description follows.

[0023] Please see Figure 1 The present invention provides a technical solution: a solid-state functional device based on the first-order magnetic phase transition step effect, comprising a magnetic phase transition functional unit and a signal interaction unit.

[0024] The magnetic phase transition functional unit is made of a material with first-order magnetic phase transition characteristics. The first-order magnetic phase transition characteristics are manifested as follows: under the induction of external excitation, the macroscopic magnetization of the material undergoes a step-like abrupt change near the phase transition point.

[0025] The signal interaction unit, coupled with the magnetic phase change functional unit through a physical field, is used to capture the energy or signal changes generated when the macroscopic magnetization intensity undergoes a step change, and convert it into an electrical, magnetic, thermal or force signal output. The signal interaction unit and the magnetic phase change function unit adopt non-contact magnetic coupling, non-contact thermal coupling, or mechanical contact coupling.

[0026] By utilizing the nonlinear abrupt change in magnetization at the phase transition critical point of primary magnetic phase transition materials, a high degree of integration of energy conversion is achieved. The magnetic phase transition functional unit, as the core of energy conversion, amplifies minute external environmental excitations into significant magnetic moment change signals. Through non-contact or mechanical coupling, the signal interaction unit effectively captures these sudden magnetic flux changes, converting them into directly usable electrical signals or other physical quantity signals. This avoids the low energy conversion efficiency of traditional devices during quasi-static conversion, improving signal response speed and signal-to-noise ratio. In some embodiments, the material of the magnetic phase change functional unit is selected from at least one of FeRh alloy, MnFePSi alloy, Ni-Mn Kihasler alloy or Fe-Pd magnetic shape memory alloy.

[0027] By selecting these specific materials, it is possible to ensure that the device obtains a large magnetic jump amplitude at the phase transition point, thereby increasing the induced electromotive force or energy density captured by the signal interaction unit, and enabling the device to be customized to match material properties for different industrial scenarios.

[0028] In some embodiments, the magnetic phase change functional unit is an epitaxially grown single-crystal thin film, and its easy magnetization axis is perpendicular to the plane of the thin film. The signal interaction unit includes an induction coil or a superconducting quantum interference device associated with the magnetic phase change functional unit through magnetic flux coupling.

[0029] The design of the easily magnetized axis perpendicular to the thin film plane ensures that the direction of magnetic flux change during a first-order magnetic phase transition is perpendicular to the sensing surface of the induction coil integrated on the thin film surface, thereby maximizing magnetic coupling efficiency. The single-crystal thin-film structure reduces grain boundary defects present in polycrystalline materials, lowers noise caused by magnetic domain wall motion, and significantly improves the device's detection sensitivity and conversion accuracy under weak field excitation.

[0030] In some embodiments, when the signal interaction unit includes an induction coil, the induction coil is disposed on the surface of the magnetic phase change functional unit to sense the instantaneous change in magnetic flux caused by the step change in macroscopic magnetization intensity and generate a pulse induced electromotive force.

[0031] According to Faraday's law of electromagnetic induction, the induced electromotive force (EMF) is proportional to the rate of change of magnetic flux over time. Because the magnetic transition time of a first-order magnetic phase transition is extremely short, a pulsed EMF with significant peak power can be generated even within a very small volume. This mechanism enables the device to output high-energy-density electrical pulses in static or extremely low-frequency environments, providing a high-quality signal source for signal extraction or energy harvesting in downstream circuits.

[0032] A system for a solid-state functional device based on the first-order magnetic phase transition step effect includes an excitation source and a management unit: the excitation source is used to provide an external energy field to drive the magnetic phase transition functional unit to undergo a first-order magnetic phase transition, and the external energy field includes at least one of a thermal field, a stress field, or a magnetic field. The management unit is electrically connected to the signal interaction unit and is configured to condition and store pulsed electrical energy in power generation mode.

[0033] The excitation source, serving as the induction terminal of the system input, ensures that the magnetic phase transition functional unit is near a metastable state through multi-field coupling, responding promptly to minor external disturbances. The management unit acts as the energy hub, and its conditioning circuitry can rectify, filter, and impedance match the narrow pulse, high-voltage, and high-bandwidth signals generated by the first-stage magnetic phase transition. In power generation mode, the system achieves the conversion and storage of high-quality pulsed electrical energy from external environmental energy, enhancing the system's practicality in energy self-sufficiency or distributed power supply.

[0034] In some embodiments, the excitation source is configured to drive the magnetic phase transition functional unit to cyclically switch between bistable states on both sides of the phase transition point, and to adjust the excitation intensity in real time through a feedback control circuit to reduce phase transition hysteresis loss; the feedback control circuit extracts part of the energy or signal from the management unit and feeds it back to the excitation source.

[0035] First-order magnetic phase transitions are typically accompanied by certain physical hysteresis losses. By modulating the excitation source in real time through a feedback control circuit, the material can achieve the maximum magnetic transition with minimal driving work within the critical region. Fine-tuning the amplitude or phase of the excitation field using electrical signals or energy feedback from the management unit effectively suppresses temperature rise and energy dissipation caused by hysteresis, ensuring the system's stability during long-term cyclic operation and improving the net energy output ratio.

[0036] In some embodiments, multiple magnetic phase transition functional units and excitation sources are configured. The system also includes a state monitoring module and a timing control module. The state monitoring module is used to monitor the magnetic state of each magnetic phase transition functional unit in real time. The timing control module is used to output time-division trigger signals to each excitation source according to the magnetic state and a preset strategy.

[0037] Through array-based design and time-division triggering logic, the system enables the collaborative operation of multiple functional units. The status monitoring module can acquire the phase transition stage of each unit in real time, avoiding repeated triggering or triggering without cooling. The timing control module, by reasonably configuring the trigger interval of each unit, transforms the overall system output from discrete pulse current to a stable pseudo-continuous current, or achieves high spatiotemporal resolution multi-point distributed sensing, greatly expanding the system's application scope in industrial power supply and complex environment monitoring.

[0038] Example 1: Pulse Power Generation Reference Figure 1 This embodiment provides a basic system for generating electrical energy using the first-order magnetic phase transition step effect. The system mainly includes an excitation source, a magnetic phase transition functional unit, and an energy extractor serving as a signal interaction unit. The magnetic phase transition functional unit is made of an alloy material with first-order magnetic phase transition characteristics (e.g., FeRh alloy). This material undergoes a phase transition between an antiferromagnetic state and a ferromagnetic state near a specific phase transition critical temperature, accompanied by discontinuous step-like abrupt changes in macroscopic magnetization. The excitation source employs a controlled thermoelectric conversion component (such as a Peltier patch), whose output end is in thermal contact with the magnetic phase transition functional unit, driving the temperature of the magnetic phase transition functional unit to periodically fluctuate around its phase transition critical temperature.

[0039] The energy extractor employs a planar helical coil structure, positioned close to the surface of the magnetic phase change functional unit. When the excitation source drives the magnetic phase change functional unit to undergo a first-order magnetic phase change, the discontinuous step-like jump in the material's magnetization intensity causes a very large instantaneous rate of change in the magnetic flux passing through the energy extractor. According to Faraday's law of electromagnetic induction, this instantaneous rate of change induces a high-amplitude pulsed electromotive force at both ends of the energy extractor, thereby realizing the conversion of environmental excitation energy into high-density electrical energy.

[0040] Example 2: Energy Self-Sustaining Circuit Reference Figure 2 Based on Example 1, this example adds an energy management unit. The energy management unit is electrically connected to the output terminal of the energy extractor and is used to rectify, store, and regulate the captured pulsed electrical energy to output stable electrical energy.

[0041] The energy management unit integrates a feedback control circuit. This circuit feeds back a portion of the electrical energy collected by the management unit to the drive circuit of the excitation source. During system operation, a portion of the electrical energy generated by the first-stage magnetic phase transition is used to supplement the excitation energy required to maintain the phase transition cycle. Through this energy feedback mechanism, the system can reduce its dependence on external energy sources, achieving self-sustaining operation or auxiliary drive under specific operating conditions, thus improving the overall energy conversion efficiency of the system.

[0042] Example 3: Array-based systems and material expansion This embodiment provides a system for multi-unit collaborative operation. The system arranges multiple power generation units, such as those in Embodiment 1 or 2, into an array. The system also includes a central controller for timing control of the excitation source 1 of each unit in the array.

[0043] Through a time-sequential triggering strategy of the central controller, each unit in the array undergoes a phase transition sequentially or alternately. This collaborative working method can superimpose and integrate the discrete pulses output by each unit on the time axis, thereby smoothing the total output power. Furthermore, the magnetic phase transition functional unit in this embodiment can be selected from at least one of FeRh alloy, MnFePSi alloy, Ni-Mn Kihasler alloy, or Fe-Pd magnetic shape memory alloy, depending on actual environmental requirements, to adapt to different excitation energy levels and operating temperature ranges.

[0044] Example 4: Chip-level Integration Example This embodiment provides a highly integrated solid-state functional device. The magnetic phase change functional unit is fabricated on a chip substrate using processes such as molecular beam epitaxy, and is a single-crystal thin film with perpendicular magnetic anisotropy, wherein its easy magnetization axis is perpendicular to the film surface direction to optimize the magnetic flux output path.

[0045] The energy extractor is fabricated into a planar microcoil using microfabrication technology and integrated with a single-crystal thin film on the same chip substrate. This achieves miniaturization and integration of the device.

[0046] Example 5: Ultra-high sensitivity temperature sensor This embodiment utilizes the first-order magnetic phase transition step effect to achieve precision sensing. Its structure adopts the chip-level integrated architecture of Embodiment 4. The magnetic phase transition functional unit is an epitaxially grown single-crystal thin film, and the signal interaction unit uses an integrated magnetoresistive detection circuit.

[0047] In this embodiment, the ambient temperature is used as an external excitation. When the ambient temperature fluctuates slightly near the phase transition point of the magnetic phase transition functional unit, it induces a dramatic change in the magnetic state inside the material. The magnetoresistive detection circuit captures the local magnetic field change caused by this change in real time and converts it into a significant change in resistance. Due to the extremely high sensitivity of the first-order magnetic phase transition, this system can achieve high-resolution monitoring of changes in ambient temperature.

[0048] Example 6: Precision Micro-actuation This embodiment utilizes the lattice distortion accompanying the first-stage magnetic phase transition to achieve displacement output. The magnetic phase transition functional unit is made of a material that exhibits volumetric jump characteristics during the first-stage magnetic phase transition (such as a Ni-Mn-based Hassler alloy single-crystal thin film). Elastic connectors are integrated onto the thin film surface using micromachining techniques, serving as the displacement transmission mechanism and constituting the signal interaction unit.

[0049] Excitation 1 employs a pulse field generator. When the excitation source drives the magnetic phase transition functional unit to switch states on both sides of the phase transition point, the step strain generated inside the material is transmitted to the external microstructure through the elastic connector, thereby driving the micro valve or optical component to produce precise micro-displacement.

[0050] like Figure 3The diagram shows the variation of magnetization with excitation. The horizontal axis is labeled "external excitation (such as temperature T / magnetic field H)," and the vertical axis is labeled "magnetization M." The near-vertical jump in the middle represents the abrupt change characteristic of the first-order magnetic phase transition.

[0051] like Figure 4 The diagram shows the timing waveforms of the working cycle, all sharing the same time axis (the horizontal axis is labeled "time t"). At the top is a square wave, representing the "excitation state". In the middle is a sharply rising and falling curve aligned with the square wave transitions, representing the "magnetic flux Φ". At the bottom is a sharp pulse waveform at the instant of magnetic flux change, representing the "induced electromotive force ε".

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A solid-state functional device based on the first-order magnetic phase transition step effect, characterized in that, Includes a magnetic phase transition functional unit and a signal interaction unit. The magnetic phase transition functional unit is made of a material with first-order magnetic phase transition characteristics. The first-order magnetic phase transition characteristics are manifested as follows: under external excitation, the macroscopic magnetization of the material undergoes a step-like abrupt change near the phase transition point. The signal interaction unit is coupled with the magnetic phase transition functional unit through a physical field to capture the energy or signal change generated when the macroscopic magnetization intensity undergoes a step change, and convert it into an electrical, magnetic, thermal or force signal output. The signal interaction unit and the magnetic phase change function unit are coupled by non-contact magnetic coupling, non-contact thermal coupling, or mechanical contact coupling.

2. A solid-state functional device based on the first-order magnetic phase transition step effect according to claim 1, characterized in that, The material of the magnetic phase change functional unit is selected from at least one of FeRh alloy, MnFePSi alloy, Ni-Mn Hassler alloy or Fe-Pd magnetic shape memory alloy.

3. A solid-state functional device based on the first-order magnetic phase transition step effect according to claim 1, characterized in that, The magnetic phase transition functional unit is an epitaxially grown single-crystal thin film, and its easy magnetization axis is perpendicular to the plane of the thin film. The signal interaction unit includes an induction coil or a superconducting quantum interference device associated with the magnetic phase transition functional unit through magnetic flux coupling.

4. A solid-state functional device based on the first-order magnetic phase transition step effect according to claim 1, characterized in that, When the signal interaction unit includes an induction coil, the induction coil is disposed on the surface of the magnetic phase change functional unit and is used to sense the instantaneous change in magnetic flux caused by the step change in macroscopic magnetization intensity and generate a pulse induced electromotive force.

5. A system for a solid-state functional device based on a first-order magnetic phase transition step effect according to any one of claims 1-4, characterized in that, Includes an excitation source and a management unit: the excitation source is used to provide an external energy field to drive the magnetic phase change functional unit to undergo a first-stage magnetic phase change, the external energy field including at least one of a thermal field, a stress field, or a magnetic field; The management unit is electrically connected to the signal interaction unit and is configured to condition and store pulsed electrical energy in power generation mode.

6. The system for a solid-state functional device based on a first-order magnetic phase transition step effect according to claim 5, characterized in that, The excitation source is configured to drive the magnetic phase transition functional unit to cyclically switch between bistable states on both sides of the phase transition point, and to adjust the excitation intensity in real time through a feedback control circuit to reduce phase transition hysteresis loss; the feedback control circuit extracts part of the energy or signal from the management unit and feeds it back to the excitation source.

7. The system for a solid-state functional device based on a first-order magnetic phase transition step effect according to claim 5, characterized in that, The magnetic phase transition functional unit and the excitation source are configured as multiple. The system also includes a state monitoring module and a timing control module. The state monitoring module is used to monitor the magnetic state of each magnetic phase transition functional unit in real time. The timing control module is used to output time-division trigger signals to each excitation source according to the magnetic state and a preset strategy.

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