Remanence coercivity

Before MFM measurements all films were characterized using magnetooptical Kerr effect millimagnetometry. That provides remanence, coercivity, and magnetic anisotropy constants. 

Table 4.17. Remanence, coercivity and energy product of some hard ferrites.

Composition Remanence Coercivity Energy Curie Maximum Hardness (HV) Alloy... 

Piezo/pyroelectric crystal or ceramic (lattice with spontaneous polarization) Ions in crystalline lattice form ionic dipoles npon symmetry breaking Ionic dipoles deform/ rotate with mechanical (electrical) stress Often also ferroelectric (hysteresis, remanence, coercive field)... 

The kinetics of the phase change can be monitored by a greater number of techniques than is available to most other systems. The individual phases can usually be seen by optical microscope, at least in single crystals. The amount of second phase can be measured instantaneously as the total charge that has passed, while the reaction rate is measured by the instantaneous current. Observations on ferroelectric specimens of incremental permittivity, initial permittivity, and hysteresis constants such as remanence, coercivity, and squareness are all useful measures of the reaction kinetics. 

Energetic analysis shows the dependence of using magnetie materials from relation of coercive force on magnetization to remanent induction. The permanent magnets... 

Figure 2 shows the two hysteresis loops for a medium and a head material. The coercivity, the saturation magnetisation, Af or iaduction, B, remanent magnetisation, M or iaduction, B, and the permeabiHty, p, differ for the two materials. 

If a very high field is appHed the magnetisation can reach its saturated state ia which all the magnetic dipoles are aligned ia the direction of the field. If the magnetic field is switched off, the remanent magnetisation M is left. If the M (or B) is then reduced to sero, a special field strength, the coercivity, is required. 

As the appHed field is reduced, the iaductioa does aot retrace curve 1 but foUows curve 2 as the domaias at first merely rotate back to the aearest local easy axis directioa. The value of B at i/ = 0 is the remanent iaductioa. At H = which is the coercive-field strength of coercive force or... 

Particulate Materials. There are three principal classes of particulate magnetic materials y-ferric oxide, y-Fe202, and its modifications chromium dioxide [12018-01 -8] and iron [7439-89-6]. A comparison of the remanent magnetization, and coercivity, for several y-Fe202... 

Hysteresis curve of a ferroelectric crystal, v = initial (virginal) curve, Pr = remanent polarization, Ps = spontaneous polarization, Ec = coercive field... 

Hysteresis curves for a magnetically hard and a magnetically soft ferromagnetic material. S = saturation magnetization, R = remanent magnetization, K = coercive force... 

Pr remanent polarization Ec coercive field. [Reprinted with permission from Ref. 114.]... 

Strength H r is needed to remove the remanence. He, the magnetic field at which Js becomes zero, is called coercive force or coercivity. Each type of magnetism shown in Figure 6.8 is associated with characteristic features which are displayed by the different Fe oxides. 

Magnet Type Maximum Energy Product kJ /m Remanence Br T Coercivity bHc kA/m... 

A second type of behavior existing in the PLZT s is the linear (Pockels) effect which is generally found in high coercive field, tetragonal materials (composition 3), This effect is so named because of the linear relationship between An and electric field. The truly linear, nonhysteretic character of this effect has been found to be intrinsic to the material and not due to domain reorientation processes which occur in the quadratic and memory materials. The linear materials possess permanent remanent polarization however, in this case the material is switched to its saturation remanence, and it remains in that state. Optical information is extracted from the ceramic by the action of an electric field which causes linear changes in the birefringence, but in no case is there polarization reversal in the material. 

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