253 results about "Residual magnetization" patented technology

A transmitter antenna assembly for transient electromagnetic well logging instrument comprises an antenna coil coupled with a current source and a magnetic core having residual magnetization. Switching current in the antenna coil results in magnetization reversal in the magnetic core and change in magnetic dipole moment of the antenna. After the magnetization reversal is complete the current is removed and the new vector of magnetic dipole of the antenna maintains constant (steady-state phase of the antenna dipole) due to magnetic hysteresis of magnetic material employed for the magnetic core. No power expenditure during the steady-state phase of the magnetic dipole facilitates highly effective generation and fast switching of a large magnetic dipole. The magnetic core also serves as a shield between the antenna coil and any conductive part of the antenna assembly. Embodiments suitable for measurement-while-drilling or measurements through casing make use of residual magnetization of magnetic drill collar or magnetic casing respectively.

An electromagnetic brake, including an electromagnetic brake actuator coil surrounding a power input shaft for a multiple-ratio transmission in a vehicle powertrain, is disclosed. An electromagnetic flux flow path for the actuator coil is electromagnetically isolated from the power input shaft and other elements of the powertrain thereby avoiding residual magnetization.

A nuclear magnetic resonance sensing apparatus and method for operating in an earth borehole comprises a source of switchable magnetic field to polarize nuclei in the region of interest, said source comprising a coil wound on a magnetic core having controllable residual magnetization. Maintaining the magnetization of the core during a polarization interval does not require steady current in the coil. Switching intensity and polarity of magnetization of the core causes precession of spin magnetic moments of the nuclei; the precession induces a signal indicative of nuclear magnetic resonance properties of earth formations.

A magnetic carrier constituting a two-component developer for use in an electrophotographic image forming method is formed of a carrier core comprising a first resin and magnetic fine particles dispersed in the first resin, and a second resin surface-coating the carrier core. (a) The magnetic carrier has a true specific gravity of 2.5-4.5, a magnetization sigma 1000 as measured in a magnetic field of 1000x(103/4 pi )xA/m (1000 oersted) of 15-60 Am2/kg (emu/g), a residual magnetization sigma r of 0.1-20 Am2/kg (emu/g) and a resistivity of 5x1011-5x1015 ohm.cm. (b) The first resin has a polymer chain including a methylene unit (-CH2-). (c) The second resin has at least a fluoro-alkyl unit, a methylene unit (-CH2-) and an ester unit. (d) The carrier core is surface-coated with (i) a mixture of the second resin and a coupling agent having at least an amino group and a methylene unit, or (ii) a coupling agent having at least an amino group and a methylene unit, and then with the second resin.

A perpendicular magnetic recording medium has a substrate, a magnetic functional layer provided on the substrate, and a magnetic recording layer stacked in contact with the magnetic functional layer and having perpendicular magnetic anisotropy. −4×2πMs²≦Ku≦6×2πMs² is satisfied, wherein Ku represents a perpendicular magnetic anisotropy constant of the magnetic functional layer and Ms represents a saturation magnetization. The magnetic moment of the magnetic functional layer is rotated in a direction of an applied magnetic field during the recording, and the magnetic moment acts on the magnetization of the recording layer in such a manner that the applied magnetic field is assisted thereby. Minute magnetic domains can be stably retained and excellent thermal disturbance resistance can be obtained.

On a single chip are formed a plurality of magnetoresistance effect elements provided with pinned layers having fixed magnetization axes in the directions that cross each other. On a substrate 10 are formed magnetic layers that will become two magnetic tunnel effect elements 11, 21 as magnetoresistance effect elements. Magnetic-field-applying magnetic layers made of NiCo are formed to sandwich the magnetic layers in plan view. A magnetic field is applied to the magnetic-field-applying magnetic layers. The magnetic field is removed after the magnetic-field-applying magnetic layers are magnetized in the direction shown by arrow A. As a result of this, by the residual magnetization of the magnetic-field-applying magnetic layers, magnetic fields in the directions shown by arrows B are applied to the magnetic layers that will become magnetic tunnel effect elements 11, 21, whereby the magnetization of the pinned layers of the magnetic layers that will become magnetic tunnel effect elements 11, 21 is pinned in the directions shown by arrows B.

A magnet roll has a plurality of magnetic poles on a surface with at least one magnetic pole portion being composed of an anisotropic bonded magnet including magnet powder and binder resin. The anisotropic bonded magnet contains R-T-N magnet powder, wherein R is at least one rare earth element including Y, Sm being indispensable, and T is Fe or Fe and Co. The R-T-N magnet powder may also contain inevitable impurities such as C, O and H. The binder resin constitutes 20-70% of the volume of the anisotropic bonded magnet such that the anisotropic bonded magnet have a maximum energy product (BH)max of 10 MGOe or more and a residual magnetization Br of 2800 G or more.

An additive to be used for raising the residual magnetism of ferrite in permanent magnetism adds an additive of raising the residual magnetism with the molecular formula of MxSiyO2, where X=1=4, y=0-2, Z=2-6 in addition to add calcium carbonate and 1-4 additives of kaolin silica, aluminium oxide and boracic acid to increase its coercive force in the secondary process during production course of strontium ferrite or barium ferrite, where X, Y and Z can be decimal and M is one or more kinds of mixtures of Fe, Pr, Nd, Mn, Sr and C. With the same raw material, by use of the additive of MxSiyO2 ofthe present invention, the residual magnetism can be raised by 50-150 Gs based on 3600-4100 Gs.

A current sensor includes a magnetoresistive element and magnetic shields arranged between a current line and the magnetoresistive element. The magnetic shields include a flat first magnetic shield placed so as to attenuate the strength of an induction magnetic field applied to the magnetoresistive element and a flat second magnetic shield placed apart from the first magnetic shield in a direction in-plane with the main surface of the first magnetic shield so as to attenuate the strength of the induction magnetic field applied to the magnetoresistive element and reduce the influence of residual magnetization in the first magnetic shield.

The invention relates to a sectional type Halbach array permanent magnet motor magnetic field calculation method. The sectional type Halbach array permanent magnet motor magnetic field calculation method comprises the steps of determining solution areas, respectively building Laplace's equations or Poisson's equations for the different solution areas, calculating the interval between magnetic blocks of a sectional type Halbach array, solving the radial and tangential component amplitudes under each order of harmonic waves of residual magnetization intensity of a permanent magnet, solving the built Laplace's equations or Poisson's equations, obtaining an expression of a scalar magnetic potential in the solution areas, and further obtaining radial and tangential components of flux densities of the areas. The sectional type Halbach array permanent magnet motor magnetic field calculation method can accurately solve the magnetic field of an inner and outer rotor sectional type Halbach array permanent magnet motor with any magnetic block number of each pole and any number of pole pairs.

The invention provides a method for preparing a nanocomposite material by assembling ferriferrous oxide in a halloysite tube, and belongs to the technical field of deep processing of nonmetallic minerals. The method comprises the following four steps: (1) pretreatment, tube expansion and purification of the halloysite minerals; (2) modification in the halloysite tube; (2) preparation of Fe3O4 magnetic nanoparticles through a mixed hydrothermal solution technology; and (4) vacuum impregnation for obtaining the compoiste material with the nano-Fe3O4 assembled in the halloysite tube. The halloysite/Fe3O4 composite material prepared in the invention has no residual magnetization or coercive force, and has a typical paramagnetic performance. The material prepared through the method has good biocompatibility, and broadens the application prospect of mineral magnetic materials in the fields of biomedicines and composite magnetic materials.

A porous ferrite core material for an electrophotographic developer, the porous ferrite core material including Mg in a content of 0.3 to 3% by weight, Ti in a content of 0.4 to 3% by weight and Fe in a content of 60 to 70% by weight, and the porous ferrite core material having a pore volume of 0.04 to 0.16 ml/g, a peak pore size of 0.4 to 1.6 μm, a saturation magnetization of 40 to 80 Am²/kg, a remanent magnetization of less than 7 Am²/kg and a coercive force of less than 43 A/m; a resin-filled ferrite carrier for an electrophotographic developer obtained by filling a resin in the voids of the porous ferrite core material; and an electrophotographic developer using the ferrite carrier.

The invention discloses a hexagonal sintered permanent magnetic ferrite magnet and a preparation method thereof and belongs to the field of permanent magnetic ferrite magnets. The composition formula of the hexagonal sintered permanent magnetic ferrite magnet is represented as A<2+>(1-x-y)B<1+>yLa<3+>xFe<3+>(n-z)Co<2+>zO<2->19, A is at least one of divalent alkaline earth metal Ca, Sr and Ba, B is at least one of univalent alkali metal Li, Na and K, x, y, z and n represent adding proportions of elements respectively, wherein x is 0.24-0.45, y is 0.03-0.10, z is 0.20-0.33, n is 10.0-12.0, x is larger than or equal to 1.1z and smaller than or equal to 1.8z, and the sum of y and z is smaller than or equal to x. The preparation method of the hexagonal sintered permanent magnetic ferrite magnet comprises steps as follows: material mixing, pre-sintering, coarse crushing, ball milling, forming, sintering and the like. The magnet has an M type magnetoplumbite structure basically and has higher residual magnetization and higher intrinsic coercivity/squareness ratio (Hk/Hcj) than a traditional permanent magnetic ferrite magnet, and the magnetic performance is remarkably optimized.

The present invention relates to a magnetic recording medium comprising a magnetic layer comprising a ferromagnetic powder and a binder on a nonmagnetic support, wherein the magnetic layer has a thickness δ ranging from 10 to 80 nm, a product, Mrδ, of a residual magnetization Mr of the magnetic layer and the thickness δ of the magnetic layer is equal to or greater than 1 mA but less than 5 mA, a ratio, Sdc/Sac, of an average area Sdc of magnetic clusters in a DC demagnetized state to an average area Sac of magnetic clusters in an AC demagnetized state as measured by a magnetic force microscope, MFM, ranges from 0.8 to 2.0.

Method and apparatus for removing residual magnetization in a data transducer, such as a recording head used to write data to a recording medium in a data storage device. A residual magnetization sense circuit senses a residual magnetization of a pole of the data transducer as a result of the application of a data transmission current to the transducer. A demagnetization current generator removes the residual magnetization by supplying the transducer with a demagnetizing current that decreases to a final magnitude in accordance with a selected profile. The demagnetization current preferably comprises a bi-directional, time varying current of selected frequency to the transducer that tapers linearly, exponentially or in a step-wise fashion to the final magnitude. The demagnetization profile is preferably continuously adapted during operation. Preferably, the sense circuit and demagnetization current generator are incorporated into a preamplifier/driver circuit which performs the demagnetization operation in a self-contained fashion.