332 results about "Ferromagnetic resonance" patented technology

A method of operating a magnetoresistive device is described. The device comprises a ferromagnetic region configured to exhibit magnetic anisotropy and to allow magnetisation thereof to be switched between at least first and second orientations and a gate capacitively coupled to the ferromagnetic region. The method comprises applying an electric field pulse to the ferromagnetic region so as to cause orientation of magnetic anisotropy to change for switching magnetisation between the first and second orientations.

This invention discloses a method and a device for selecting single-phase fault of small earth current nets, which integratedly processes multiple kinds of fault signals based on the earth situation of the non-earth and arc-extinguishing coils, applies multiple kinds of line selention criteria to constitute quantification espressions showing that a line may be a fault one to get the final line selection result by integrated judgment, the selection device has good man-machine interface and is easily operated and installed, the hardware of the device is a PCI bus industrial control mainboard, and the selection algorithm is realized by virtual instrument technology to differentiate faults of single-phase earth, breakage of voltage mutual-inductors and ferromagnetic resonance and displayed by LCD.

Provided is a thin-film magnetic head capable of writing data with high accuracy on a magnetic recording medium having high coercive force without heating. The head comprises an electromagnetic coil element comprising: a main magnetic pole; an auxiliary magnetic pole; and a write coil formed so as to pass through at least between the main magnetic pole and the auxiliary magnetic pole, for generating the write magnetic field. In this head, a part of the write coil has a layered structure of: a resonance coil layer for generating a resonance magnetic field having ferromagnetic resonance frequency of a magnetic recording layer of a magnetic recording medium or having a frequency in the vicinity thereof; and a write coil layer. And further, the resonance coil layer and the write coil layer sandwich an insulating layer therebetween.

The invention discloses a unipolar current-voltage integration sensor, relating to an electronic sensor in the field of intelligent power grids. The sensor comprises a current sensor, a voltage measurement sensor, a voltage correction sensor, a signal modulation circuit, an A / D (Analog to Digital) conversion circuit, an FPGA (Field Programmable Gate Array) unit, a wireless transmission extension unit and a high-voltage electricity getting device. A current signal of a power transmission line is collected by the three sensors and the signal is processed. After a voltage value of tested current is calculated, detection information is transmitted through a wireless communication network. The high-voltage electricity getting device can be used for supplying electric energy to online monitoring equipment for a long time by getting energy through a current transformer and cooperatively supplying power with a lithium cell. According to the unipolar current-voltage integration sensor disclosed by the invention, current and voltage information can be transmitted to the computer to be subjected to data processing rapidly, integrally and accurately; high voltage, large current and ferromagnetic resonance cannot be generated; the sensor can be conveniently connected with an electronic instrument and micro-computer measurement and control protection equipment; the system structure is simplified; the space is saved; the energy consumption is very low; and the stability and the accuracy of the whole system are improved.

To realize an electric field-driven type ferromagnetic resonance excitation method of low power consumption using an electric field as drive power, and provide a spin wave signal generation element and a spin current signal generation element using the method, a logic element using the elements, and a magnetic function element such as a high-frequency detection element and a magnetic recording device using the method. A magnetic field having a specific magnetic field application angle and magnetic field strength is applied to a laminate structure in which an ultrathin ferromagnetic layer sufficiently thin so that an electric field shield effect by conduction electrons does not occur and a magnetic anisotropy control layer are directly stacked on each other and an insulation barrier layer and an electrode layer are arranged in order on an ultrathin ferromagnetic layer side. An electric field having a high-frequency component of a magnetic resonance frequency is then applied between the magnetic anisotropy control layer and the electrode layer, thereby efficiently exciting ferromagnetic resonance in the ultrathin ferromagnetic layer.

A high sensitivity magnetic anomaly detector for geomagnetic exploration comprises a shorted coaxial transmission line having as central conductor an amorphous magnetic wire. A static magnetic field is applied along the transmission line. A transverse electromagnetic wave also propagates along the transmission line and excites a ferromagnetic resonance of the magnetic ions located within the depth of penetration of the circumferential microwave magnetic field into the magnetic wire. The microwave giant magnetoimpedance effect occurring in the magnetic wire changes the magnetic wire impedance as follows: the real part of the impedance peaks and the imaginary part passes through zero at a given frequency (the ferromagnetic resonance frequency). This frequency depends on the saturation magnetization of the magnetic wire and the strength of the static magnetic field. A slight variation of the Earth's magnetic field (a magnetic anomaly) changes this frequency, thus providing information about large metallic masses hidden under the Earth's surface or underwater.

The invention provides a quick diagnostic and processing method of power distribution network ferromagnetic resonance and one-phase earth faults. When a power grid operation mode changes, firstly, excitation reactance Xp of an electromagnetic type voltage transformer of a transformer substation bus system is typed in a computer measure and control unit, then a power grid tracking measurement branch circuit is used for carrying out tracking measurement on the system capacitive reactance value of the power grid operation mode, if the system capacitive reactance value meets a power grid ferromagnetic resonance condition is judged, and resonance condition dynamic early-warning is carried out. When power grid neutral point displacement voltages are abnormal, an earth current compensation and detection branch circuit is adopted to detect zero sequence currents of a loop, and according to the magnitude of the zero sequence currents, ferromagnetic resonance and one-phase earth judgement is carried out. When it is judged that ferromagnetic resonance faults happen, a resonance eliminating branch circuit is switched for eliminating resonance, and when it is judged that one-phase earth faults happen, the zero sequence current method is used for selecting a fault line.

A left-handed composite material which includes a mixture of a ferromagnetic material and a dielectric material. The direction of magnetization of the ferromagnetic material, and its volume fraction are controlled such that the composite material exhibits negative permeability in a frequency region near the ferromagnetic resonance frequency, and low eddy current losses. Furthermore, the handedness of the material may be locally tuned to be alternately converted into a right-handed material or a left-handed material by application of an external magnetic field, electric field, or mechanical stress. Such materials are easy to make and can be easily scaled up for industrial use.

The invention discloses a method of eliminating ferromagnetic resonances. A sine fitting algorithm is utilized to identify ferromagnetic resonances and one-phase grounding faults, according to the method, zero sequence voltage sampling data are subjected to fitting, whether zero sequence voltages are in fundamental frequency quantity can be judged according to the amplitude of a fitting function, wave distortion characteristics of the zero sequence voltages in the fundamental resonances are utilized to construct a wave distortion degree function, and degrees of wave distortion are calculated to distinguish the fundamental resonances and the one-phase grounding. The method has the advantages of being simple in principle, small in calculation amount, and high in sensitivity, the fundamental resonances and the one-phase grounding are accurately distinguished, and moreover ferromagnetic resonance faults are eliminated.

The invention relates to an equivalent circuit model building method of transformer iron cores in different structures. The equivalent circuit model building method includes steps that: (1) the magnetic field intensity and the magnetic induction intensity of iron core materials are calculated through a Jiles-Atheron model; (2) equivalent circuit models of transformers with different iron core structures are constructed according to the duality principle; and (3) parameters of the equivalent circuit models of the transformers are calculated. According to the equivalent circuit model building method, parameters of the JA model are solved through hysteresis loop data of the iron core materials and serve as input of a duality principle model. The equivalent circuit models capable of calculating excitation characteristic changing of the transformers with different iron core structures on the condition of direct current magnetic bias are built by aid of the duality between a magnetic circuit and currents and can simulate transformer direct current magnetic bias, magnetizing inrush currents, ferromagnetic resonance and the like.

The invention discloses a system and method for identification and inhibition of ferromagnetic resonance of a medium-voltage power distribution network. The method includes the following steps: installing an active inversion device between a neutral point of the medium-voltage power distribution network and the ground; monitoring a bus zero sequence voltage of the medium-voltage power distribution network in a real-time manner and when the zero sequence voltage is larger than 10% of a rated phase voltage, detecting whether ferromagnetic resonance happens in the medium-voltage power distribution network; if the ferromagnetic resonance happens in the medium-voltage power distribution network, the active inversion device injecting zero sequence current signals to the medium-voltage power distribution network and tracking the zero sequence voltage and changing the intensity and direction of zero sequence current in a real-time manner so as to enable the zero sequence voltage to be zero and force the medium-voltage power distribution network to break away from a ferromagnetic resonance state; and then stopping injection of the zero sequence current so as to enable the medium-voltage power distribution network to return to a normal operation state. The system and method inhibit ferromagnetic resonance through short-time injection of the zero sequence current by the active inversion device so that inhibition of low-frequency ferromagnetic resonance, power frequency ferromagnetic resonance and high-frequency ferromagnetic resonance can be realized rapidly and the system and method have the advantages of being rapid and efficient, simple and convenient in operation, practical and economical and zero in effect on normal operation of the medium-voltage power distribution network and the like.

The invention discloses a high-power yttrium-gadolinium garnet ferrite having the composition chemical formula specifically expressed as Sm[x]Y[3-x-y-2z-p-q-q']Gd[y]Ca[2z+p+q+q']V[z]Ge[p]Sn[q]Ti[q']In[q'']Al[w]Mn[w']Fe[5-z-p-q-q'-q''-w-w'-[delta]]O[12], wherein 0<=x<=0.20, 0<=y<=3.0, 0<=z<=1.3, 0<=p<=0.9, 0<=q<=0.7, 0<=q'<=0.7, 0<=q''<=0.70, 0<=w<=1.3, 0<=w'<=0.10, 0<=delta<=0.8, and delta represents iron deficient quantity. The high-power garnet ferrite material having high spin wave line width [delta]Hk, low ferromagnetic resonance line width [delta]H and high dielectric constant epsilon' can be obtained.

A garnet ferrite for a non-reciprocal circuit element expressed by the formula Y3-xGdxFet-2y-zCoySiyAlzO12 (where 0.2<=x<=1.5, 0.005<=y<=0.015, 0<=z<=1.5, 4.75<=t<=5) is provided. The absolute temperature coefficient alphaof 4piMs and the ferromagnetic resonance half-width DeltaH are low. In addition, an isolator is provided, wherein the isolator includes a magnetic assembly made up of a main body (the garnet ferrite element) and a plurality of center conductors disposed on the upper surface of the main body so that each of the center conductors intersect at a predetermined angle while being electrically insulated from each other, a magnet for applying a direct current magnetic field to the magnetic assembly, matching capacitors, and a yoke (upper and lower cases) for holding all the components. Loss is low in a high-frequency band, such as the microwave band.

RFID tags and devices disclosed herein use ferromagnetic films to store information. The tags include patches of ferromagnetic materials, each patch having a particular ferromagnetic resonance frequency determined by the composition of the ferromagnetic film. When stimulated, the patches emit microwave or RF signals at their resonance frequencies and at intensities proportional to the patch sizes. The signals are read and the frequency spectrum of the tag may be determined by using a FFT. Identity and other information may be provided by the spectrum.

The invention relates to a ferromagnetic resonance failure detection method of a neutral point ungrounded system. With the method, bus three-phase voltage and zero-sequence voltage signals are analyzed to detect ferromagnetic resonance failures of a system, a plurality of harmonic waves of adjacent frequency components are contained in the neutral point ungrounded system within 0.1s in the initial stage of ferromagnetic resonance, while only 50Hz of frequency component is contained in single-phase ground failure within 0.1s while the failure occurs, and the ferromagnetic resonance and the single-phase ground failure are distinguished at the initial stage of failure according to the essential difference of the ferromagnetic resonance failure and the single-phase ground failure, and then the resonance type of the ferromagnetic resonance is further detected. Atom decomposition method is taken as a ferromagnetic resonance signal analysis tool, a highly redundant atom library can capture natural characteristics of signals well, sparse decomposition of the signals is realized, and the representing result of the signals is concise and reliable.

The invention discloses a hexagonal ferrite material with high anisotropy and low ferromagnetic resonance line width and a preparation method and belongs to the technical field of preparation of ferrite materials. The material is prepared from a main component and a dopant and is characterized in that the main component comprises 67.0mol%-75.0mol% of Fe2O3, 0.5mol%-7.5mol% of SrCO3, 0.5mol%-7.5mol% of BaCO3, 3.5mol%-6.5mol% of Co2O3, 3.5mol%-11.5mol% of La2O3 and 8.5mol%-13.5mol% of CuO; the dopant comprises, in percentage by weight of the main component in terms of oxide, 0.5wt%-2.0wt% of Bi2O3, 0.15wt%-1.0wt% of B2O3, 0.02wt%-0.32wt% of CaCO3, 0.02wt%-0.32wt% of SiO2 and 0.05wt%-0.50wt% of ISOBAM. The ferrite material has the characteristics of high density d larger than 5.20 g / cm<3>, high remanence 4 phi Mr larger than 4.3 kGs, high anisotropic field Ha larger than 15.0 kOe and low ferromagnetic resonance line width delta H smaller than 3,700 e (@44 GHz and Zero field).

The present invention relates to a resonance elimination apparatus and method of ferromagnetic resonance, wherein the apparatus is electrically connected to an electromagnetic voltage transformer in a power distribution network, and comprises: a power source module, a resonance judging module, a resonance elimination module, and a current transformer, wherein the power source module is electrically connected to the resonance judging module and the resonance elimination module; the current transformer is electrically connected to a connecting wire between a neutral point of the electromagnetic voltage transformer and the earth, and the current transformer is electrically connected to the resonance judging module; the resonance elimination module comprises a resonance elimination resistor and a first control switch, both ends of the resonance elimination resistor are connected to both ends of an open triangular loop of the electromagnetic voltage transformer in series, the first control switch is connected between the resonance elimination resistor and the open triangular loop in series; and the resonance judging module is electrically connected to the first control switch. The apparatus provided in this embodiment can accurately and fast eliminate ferromagnetic resonance and improve resonance elimination efficiency of ferromagnetic resonance.

The invention belongs to the technical field of magnetic materials, and discloses a high-stability garnet microwave ferrite magnetic sheet and a preparation method thereof. The material composition ofthe high-stability garnet microwave ferrite magnetic sheet is Y<3-f-2d-a>Gd<f>Ca<2d+a>Bi<e>Fe<5-a-b-c-d-sigma>SnInMn<c>V<d>O<12>, wherein a is more than 0 and no more than 0.7; b is more than 0and no more than 0.7; c is more than 0 and no more than 0.6; d is more than 0 and no more than 1.5; e is more than 0 and no more than 0.6; f is more than 0 and no more than 0.8; and sigma is more than 0 and no more than 0.4. According to the high-stability garnet microwave ferrite magnetic sheet, Bi<3+> ions are added into the material, so the dielectric constant of the material is improved, anda Curie temperature is increased; and in addition, SnO<2>, In<2>O<3>, SnO<2> and In<2>O<3> are added into the material, so the anisotropy coefficient K of the material can be reduced, and the ferromagnetic resonance linewidth Delta(H) of the material is reduced. In terms of the process, high-pressure sintering is adopted to replace normal-pressure sintering, so sintering density is improved, the porosity of the material is reduced, and the ferromagnetic resonance linewidth Delta(H) of the material is reduced. Thus, the problem that the temperature coefficient of the material is poor is solved,and the material is guaranteed to have low ferromagnetic resonance linewidth Delta(H), high dielectric constant and high Curie temperature.

Belonging to technical field of control and protection, the controllable damping device includes damping reactor, inverse parallel controllable silicon, triggering controller. Damping reactor and inverse parallel controllable silicon are cascaded to constitute a damping control main circuit, which is connected to port of triangle winding at opening of PT secondary side. Advantages are that the invention can distinguish resonance fault from singlephase earth fault to implement correct damping control of resonance as well as indicate which fault including faults of frequency division, basic frequency, ferro resonance in high frequency and single phase grounding occurs in system correctly. The device does not influence on normal operation of electric network and collection of system zero sequence signal, does not generate higher harmonic and other interference signal.

The invention discloses a garnet ferrite material without rare earth and belongs to the technical field of microwave ferrite materials. The garnet ferrite material has a chemical formula being Bi(3-(2a+b+c+m+n))Ca(2a+b+c+m+n)VaZrbSncIndTimGenFe(5-a-b-c-d-m-n-delta)O12, wherein a is larger than or equal to 0 and smaller than or equal to 1, b is larger than or equal to 0 and smaller than or equal to 1, c is larger than or equal to 0 and smaller than or equal to 0.8, d is larger than or equal to 0 and smaller than or equal to 0.7, m is larger than or equal to 0 and smaller than or equal to 1, and delta denotes the iron deficiency amount and is larger than or equal to 0.02 and smaller than or equal to 0.5. The invention also discloses a preparation method of the material. Tests prove that the garnet ferrite material without rare earth has the dielectric constant epsilon larger than or equal to 20, the ferromagnetic resonance linewidth delta H smaller than or equal to 7 kA / m and the dielectric loss tg delta epsilon smaller than or equal to 0.0005. The garnet ferrite material has the characteristics of low cost, high dielectric constant and the like and can be used for solving the problem of miniaturization of microwave devices. The preparation method adopts a reasonable process and is suitable for popularization and application, material consumption can be reduced, and the cost is further reduced.

Systems and methods are provided for controlling coherence of a magnetic resonance signal of spin species. The small difference between hard π pulses and their delta-function approximation is exploited to provide new classes of spin echoes which have applications in nuclear magnetic resonance (NMR) spectroscopy, magnetic resonance imaging (MRI) and magnetic resonance microscopy (MRM), and related spectroscopies of solids, and mixtures of solids and liquids. Systems and methods are also provided for controlling coherence of the resonance signal from pseudospin species.

RFID tags and devices disclosed herein make use ferromagnetic films to store information. The tags include patches of ferromagnetic materials, each patch having a particular ferromagnetic resonance frequency determined by the composition of the ferromagnetic film. When stimulated, the patches emit microwave or RF signals at their resonance frequencies and at intensities proportional to the patch sizes. The signals are read and the frequency spectrum of the tag may be determined by using a FFT. Identity and other information may be provided by the spectrum.

To realize an electric field-driven type ferromagnetic resonance excitation method of low power consumption using an electric field as drive power, and provide a spin wave signal generation element and a spin current signal generation element using the method, a logic element using the elements, and a magnetic function element such as a high-frequency detection element and a magnetic recording device using the method. A magnetic field having a specific magnetic field application angle and magnetic field strength is applied to a laminate structure in which an ultrathin ferromagnetic layer sufficiently thin so that an electric field shield effect by conduction electrons does not occur and a magnetic anisotropy control layer are directly stacked on each other and an insulation barrier layer and an electrode layer are arranged in order on an ultrathin ferromagnetic layer side. An electric field having a high-frequency component of a magnetic resonance frequency is then applied between the magnetic anisotropy control layer and the electrode layer, thereby efficiently exciting ferromagnetic resonance in the ultrathin ferromagnetic layer.

The present invention provides an yttrium-iron-garnet single-crystal film and a liquid-phase epitaxy preparation method thereof, and belongs to the field of electronic materials. According to the present invention, the component of the yttrium-iron-garnet single-crystal film is La[x]Y[3-x]Fe5O12, wherein x is 0.01-0.05; 0.44% by mass of Y2O3, 10.31% by mass of Fe2O3, 0.06% by mass of La2O3, 87.44% by mass of PbO and 1.75% by mass of B2O3 are adopted as raw materials; the liquid-phase epitaxy method is used to grow the single-crystal film; the ferromagnetic resonance line width of the obtained yttrium-iron-garnet single-crystal film is narrow and achieves less than or equal to 1 Oe; and the roughness, the lattice matching, the film stress, the lead content, the impure phase and the like of the film are improved.

System, apparatus and method for performing magnet resonance imaging. The apparatus comprises first and second members for distributing the weight of a patient to be imaged in a substantially upright position between the patient's knees and buttocks. The system comprises a horizontal field magnet magnetic resonance imaging apparatus in combination with the apparatus. In accordance with the method a patient is imaged in an ergonomic position with the patient's weight distributed between the patient's buttocks and knees.

The invention aims at solving the technical problem of providing a LiZnTi ferrite material which is low in coercivity, low in ferromagnetic resonance linewidth and high in saturation magnetization intensity property under the circumstance of satisfying sintering at a low temperature below 950 DEG C; the LiZnTi ferrite material is used for an LTCC (Low Temperature Co-fired Ceramic) phase shifter. The ferrite material is composed of a main material and a glass phase sintering aid, wherein the percentage by weight of the main material is 99.3-99.85%, while the percentage by weight of the glass phase sintering aid is 0.15-0.7%; the main material is prepared from raw materials Li2CO3, ZnO, TiO2 and Fe2O3 according to a molecular formula Li0.43Zn0.27Ti0.13Fe2.17O4; the glass phase sintering aid is prepared by mixing 52.45mol% of Li2O, 31.06mol% of B2O3, 11.99mol% of SiO2, 2mol% of CaO and 2.5mol% of Al2O3 together, performing ball milling on the mixture for 12 hours, heating to 1150 DEG C and preserving heat for 1 hour, reducing to 1000 DEG C and carrying out quick quenching. The preparation method of the ferrite material has the advantages that the sintering temperature of the LiZnTi ferrite is successfully reduced to about 900 DEG C and the excellent gyromagnetism of the LiZnTi ferrite material is kept, and therefore, the material can be co-fired with a silver electrode and widely applied to manufacturing the LTCC phase shifters.

The invention provides a diagnostic method for ferromagnetic resonance in a neutral non-grounding 10kV system. A phase-A voltage to ground, a phase-B voltage to ground, a phase-C voltage to ground, a neutral point voltage and a neutral point frequency are caught when the voltage at the two ends of a PT opening triangle exceeds the set limiting value. Firstly, faults are divided into a frequency division resonance and high frequency resonance class and a fundamental resonance and high frequency resonance class, then, frequency division resonance and high frequency resonance are distinguished according frequencies, the type of fundamental resonance and single-phase ground faults is processed according to an energy method and a loop grounding current method, and the preliminary conclusion is obtained through the energy method and then is checked through the loop grounding current method; when the results obtained through the two methods are the same, it is shown that judgment is correct, and the fundamental resonance and single-phase ground faults are distinguished. The distinguished faults and the obtained non-ferromagnetic resonance and single-phase ground fault conclusions are sent to a terminal to be displayed, and maintainers can process the corresponding faults in time.

A thin-film magnetic head having microwave magnetic exciting function, includes a write magnetic field production unit for producing, in response to a write signal, a write magnetic field to be applied into a magnetic recording medium, a line conductor of a microwave radiator of a plane-structure type, formed independent from the write magnetic field production means, for radiating, by feeding there through a microwave excitation current, a microwave band resonance magnetic field with a frequency equal to or in a range near a ferromagnetic resonance frequency FR of the magnetic recording medium, and two conductors separated from the line conductor in a direction perpendicular to a track-width direction of the thin-film magnetic head and parallel to an ABS of the thin-film magnetic head. The microwave radiator is an inverted micro strip waveguide having the line conductor and a ground conductor constituted by the magnetic recording medium. A section of the line conductor, perpendicular to the track-width direction has a rectangular shape. An aspect ratio B / A is within a region from 0.15 to 1.2 or within a region of 7 or more, where A is a length in a lateral direction of the line conductor, which is in parallel with the ABS and perpendicular to the track-width direction, and B is a length in a longitudinal direction of the line conductor, which is perpendicular to the air bearing surface.

An MR element having a magnetically free layer and a magnetic bias layer that applies a bias magnetic field to the magnetically free layer are included. Furthermore, a measuring section that measures a ferromagnetic resonance frequency f0 of the magnetically free layer under a condition of applying a predetermined external magnetic field Hm to the magnetically free layer, and an operation section that computes the bias magnetic field Hb according to a following conditional expression (1):Hb={(2*π*f0 / γ)2 / Ms}−(Hk+Hm)  (1)where γ is a gyroscope constant, Ms is a saturation magnetic field of the magnetically free layer, and Hk is a shape anisotropy magnetic field of the magnetically free layer.