(See related pages)
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| Ferromagnetic material | one that is capable of being highly magnetized. Elemental iron, cobalt, and nickel are ferromagnetic materials. (See page(s) 869; Sec 15.1) |
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| Magnetic field | the magnetic field produced by an external applied magnetic field or the magnetic field produced by a current passing through a conducting wire or coil of wire (solenoid). (See page(s) 869; Sec 15.1) |
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| Magnetization | a measure of the increase in magnetic flux due to the insertion of a given material into a magnetic field of strength H. In SI units the magnetization is equal to the permeability of a vacuum (μ0) times the magnetization, or μ0M. (μ0 = 4π × 10-4 T · m/A.) (See page(s) 869; Sec 15.1) |
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| Magnetic induction | the sum of the applied field H and the magnetizationMdue to the insertion of a given material into the applied field. In SI units, B = μ0(H + M). (See page(s) 869; Sec 15.1) |
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| Magnetic permeability | the ratio of the magnetic induction B to the applied magnetic field H for a material; μ = B/H. (See page(s) 869; Sec 15.1) |
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| Relative permeability | the ratio of the permeability of a material to the permeability of a vacuum; μr = μ/μ0. (See page(s) 869; Sec 15.1) |
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| Magnetic susceptibility | the ratio of M (magnetization) to H (applied magnetic field); Χm = M/H . (See page(s) 869; Sec 15.1) |
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| Diamagnetism | a weak, negative, repulsive reaction of a material to an applied magnetic field; a diamagnetic material has a small negative magnetic susceptibility. (See page(s) 869; Sec 15.2) |
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| Paramagnetism | a weak, positive, attractive reaction of a material to an applied magnetic field; a paramagnetic material has a small positive magnetic susceptibility. (See page(s) 869; Sec 15.2) |
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| Ferromagnetism | the creation of a very large magnetization in a material when subjected to an applied magnetic field. After the applied field is removed, the ferromagnetic material retains much of the magnetization. (See page(s) 869; Sec 15.2) |
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| Bohr magneton | the magnetic moment produced in a ferro- or ferrimagnetic material by one unpaired electron without interaction from any others; the Bohr magneton is a fundamental unit. 1 Bohr magneton = 9.27 × 10-24 A · m2 . (See page(s) 869; Sec 15.2) |
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| Antiferromagnetism | a type of magnetism in which magnetic dipoles of atoms are aligned in opposite directions by an applied magnetic field so that there is no net magnetization. (See page(s) 869; Sec 15.2) |
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| Ferrimagnetism | a type of magnetism in which the magnetic dipole moments of different ions of an ionically bonded solid are aligned by a magnetic field in an antiparallel manner so that there is a net magnetic moment. (See page(s) 869; Sec 15.2) |
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| Curie temperature | the temperature at which a ferromagnetic material when heated completely loses its ferromagnetism and becomes paramagnetic. (See page(s) 870; Sec 15.3) |
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| Magnetic domain | a region in a ferro- or ferrimagnetic material in which all magnetic dipole moments are aligned. (See page(s) 870; Sec 15.4) |
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| Exchange energy | the energy associated with the coupling of individual magnetic dipoles into a single magnetic domain. The exchange energy can be positive or negative. (See page(s) 870; Sec 15.5) |
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| Magnetostatic energy | the magnetic potential energy due to the external magnetic field surrounding a sample of a ferromagnetic material. (See page(s) 870; Sec 15.5) |
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| Magnetocrystalline anisotropy energy | the energy required during the magnetization of a ferromagnetic material to rotate the magnetic domains because of crystalline anisotropy. For example, the difference in magnetizing energy between the hard [111] direction of magnetization and the [100] easy direction in Fe is about 1.4 × 104 J/m3 . (See page(s) 870; Sec 15.5) |
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| Domain wall energy | the potential energy associated with the disorder of dipole moments in the wall volume between magnetic domains. (See page(s) 870; Sec 15.5) |
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| Magnetostriction | the change in length of a ferromagnetic material in the direction of magnetization due to an applied magnetic field. (See page(s) 870; Sec 15.5) |
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| Magnetostrictive energy | the energy due to the mechanical stress caused by magnetostriction in a ferromagnetic material. (See page(s) 870; Sec 15.5) |
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| Hysteresis loop | the B versus H or Mversus H graph traced out by the magnetization and demagnetization of a ferro- or ferrimagnetic material. (See page(s) 870; Sec 15.6) |
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| Saturation induction or saturation magnetization | the maximum value of induction Bs or magnetization Ms for a ferromagnetic material. (See page(s) 870; Sec 15.6) |
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| Remanent induction or remanent magnetization | the value of B or M in a ferromagnetic material after H is decreased to zero. (See page(s) 870; Sec 15.6) |
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| Coercive force | the applied magnetic field required to decrease the magnetic induction of a magnetized ferro- or ferrimagnetic material to zero. (See page(s) 870; Sec 15.6) |
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| Soft magnetic material | a magnetic material with a high permeability and low coercive force. (See page(s) 870; Sec 15.7) |
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| Hysteresis energy loss | the work or energy lost in tracing out a B-H hysteresis loop. Most of the energy lost is expended in moving the domain boundaries during magnetization. (See page(s) 870; Sec 15.7) |
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| Eddy-current energy losses | energy losses in magnetic materials while using alternating fields; the losses are due to induced currents in the material. (See page(s) 870; Sec 15.7) |
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| Iron-silicon magnetic alloys | Fe-3 to 4% Si alloys that are soft magnetic materials with high saturation inductions. These alloys are used in motors and low-frequency power transformers and generators. (See page(s) 870; Sec 15.7) |
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| Nickel-iron magnetic alloys | high-permeability soft magnetic alloys used for electrical applications where a high sensitivity is required such as for audio and instrument transformers. Two commonly used basic compositions are 50% Ni-50% Fe and 79% Ni-21% Fe. (See page(s) 870; Sec 15.7) |
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| Hard magnetic material | a magnetic material with a high coercive force and a high saturation induction. (See page(s) 871 Sec 15.8) |
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| Energy product max | the maximum value of B times H in the demagnetization curve of a hard magnetic material. The (BH) max value has SI units of J/m3 . (See page(s) 871 Sec 15.8) |
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| Alnico magnetic alloys | a family of permanent magnetic alloys having the basic composition of Al, Ni, and Co, and about 25 to 50 percent Fe. A small amount of Cu and Ti is added to some of these alloys. (See page(s) 871 Sec 15.8) |
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| Magnetic anneal | the heat treatment of a magnetic material in a magnetic field that aligns part of the alloy in the direction of the applied field. For example, the α' precipitate in alnico 5 alloy is elongated and aligned by this type of heat treatment. (See page(s) 871 Sec 15.8) |
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| Rare earth magnetic alloys | a family of permanent magnetic alloys with extremely high energy products. SmCo5 and Sm(Co, Cu)7.4 are the two most important commercial compositions of these alloys. (See page(s) 871 Sec 15.8) |
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| Iron-chromium-cobalt magnetic alloys | a family of permanent magnetic alloys containing about 30% Cr-10 to 23% Co and the balance iron. These alloys have the advantage of being cold-formable at room temperature. (See page(s) 871 Sec 15.8) |
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| Soft ferrites | ceramic compounds with the general formula MO · Fe2O3, where M is a divalent ion such as Fe2+, Mn2+, Zn2+, or Ni2+. These materials are ferrimagnetic and are insulators and so can be used for high-frequency transformer cores. (See page(s) 871 Sec 15.9) |
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| Normal spinel structure | a ceramic compound having the general formula MO · M2O3 . The oxygen ions in this compound form an FCC lattice, with the M2+ ions occupying tetrahedral interstitial sites and the M3+ ions occupying octahedral sites. (See page(s) 871 Sec 15.9) |
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| Inverse spinal structure | a ceramic compound having the general formula MO · M2O3 . The oxygen ions in this compound form an FCC lattice, with the M2+ ions occupying octahedral sites and the M3+ ions occupying both octahedral and tetrahedral sites. (See page(s) 871 Sec 15.9) |
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| Hard ferrites | ceramic permanent magnetic materials. The most important family of these materials has the basic composition MO · Fe2O3 , where M is a barium (Ba) ion or a strontium (Sr) ion. These materials have a hexagonal structure and are low in cost and density. (See page(s) 871 Sec 15.9) |