Coercive Force


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coercive force

[kō′ər·siv ′fȯrs]
(electromagnetism)
The magnetic field H which must be applied to a magnetic material in a symmetrical, cyclicly magnetized fashion, to make the magnetic induction B vanish. Also known as magnetic coercive force.

Coercive Force

 

one of the characteristics of the phenomenon of hysteresis. In magnetic hysteresis the coercive force is the magnetic field intensity at which a ferromagnetic specimen that has been initially magnetized to saturation becomes demagnetized. A distinction is made between the coercive force JHc (or Hc) and the force BHc, when the magnetization J of the specimen or the magnetic induction B in the specimen becomes zero.

Coercive forces are measured by means of coercimeters. The values for ferromagnetic materials vary over a wide range, from 10-3 to 104 oersteds, or 8 x 10-2 to 8 x 105 amperes per meter (A/m). For a given magnetic material the coercive force depends to a large extent on the preparation of the specimen and on its treatment, as well as on external conditions, such as temperature. According to the magnitude of the coercive force, magnetic materials are customarily divided into magnetically soft materials (small Hc) and magnetically hard materials (large Hc). The value of the coercive force is determined by the factors that oppose remagnetization of the specimen. The presence of impurities, lattice defects, and various types of inhomogeneities in a specimen hinders the movement of domain walls and thus increases Hc.

Particularly high values of coercive force (103–104 oersteds) are achieved by single-domain ferromagnetic particles (with substantial magnetic anisotropy). The coercive force of ferroelectric materials is considered to be like that of ferromagnetic materials.

References in periodicals archive ?
The coercive force and the saturation magnetization of the sol and the gel are displayed in Figure 6.
power at the time, many have contemplated and studied Japan's reasons for what appeared to be "national suicide." (35) While it is beyond the scope of this article to dissect the substantial literature surrounding causes of war, this model asserts that armed conflict occurs when high-priority interests are not reconcilable through measures short of coercive force. (36) Analyses of the attack on Pearl Harbor present varying arguments about the direct causes of war, but it is evident that Japan and the United States had directly incompatible interests at the time: Japan sought expansion into Southeast Asia and U.S.
Herein lies one subtlety of the PLAN's coercive force at the strategic level: it would be equally reasonable for a government in the region to infer that China one day could replace the front line of CCG vessels with ASCM-armed PLAN ships.
This requires the use of coercive force by individuals, which in turn creates havoc.
This is not to suggest that all use of coercive force by unions is negative; in fact, papal encyclicals are clear about "the positive role of conflict when it takes the form of a 'struggle for social justice.'" (4) However it does suggest that unions are at their most powerful when, as Daly says, their "religious ideas helped to expose, more than resolve, profound tensions in American liberalism around labor issues generally and the place of unions in particular." The loss of this wellspring of power for labor has, paradoxically, caused the labor movement to double down on its exercise of other means of power.
He notes the decrease in other state resources such as taxes characterized by a very low recovery rate due to insecurity and weakness of the state deprived of coercive force.
In the MCM mode the silicon needles with 60 nm cobalt coating (coercive force 20-30 mT) and 20 nm chromium protective layer were used.
To me, an enemy of freedom is one who employs coercive force. Jenny McCarthy is merely exercising free speech.
The magnetic force of a magnet is in inverse proportion to its coercive force (resistance to a magnetic field on the outside), and magnetic force weakens as the temperature rises.
The following process was used, applying diagnostic parameters such as the usage of hardness, coefficient of hardness variation, coercive force, metal's magnetic memory and acoustic emission.
Through the years, criminal self-representation, in Munby's words, has "continually engaged with the violent and coercive force of racial subordination" (181).
The results indicate that the saturation magnetization and coercive force of iron NWs are 157.93 emu/g and 9.74 Oe, respectively.