Coercitive field

When the electric field is higher than the coercitive field strength, the spontaneous polarisation is switched and the dipoles reorientate along the field lines. This process of domain switching for Eei=Ec can be described in three steps i) nucleation of an anti-parallel domain, ii) domain growth and iii) saturation of the polarisation [461, 462]. 

Fig. 51 Schematic macroscopic hysteresis loop of a ferroelectric material. Therein Ec denotes the coercitive field strength, Prei the remanent polarisation and P ei the saturation polarisation...

FIGURE 13. Coercitivity field strength (//D as function of the Ag concentration for self-assembled [Pto.4vFeo.53]ioo-iAg c nanoparticles annealed at 500 °C. Reproduced from Reference 96 by permission of the American Institute of Physics... 

The near-vertical portions of the loop in Figure 8.5 correspond to the reversal of the spontaneous polarization when opposite 180°-domains nucleate and grow. The near-horizontal portions represent saturated single-domain states. The remanent polarization (E = 0) shown is about 0.27Cm , the coercitive field strength... 

Subsequently, a series of related compounds of formula (NBU4)-[MCrloxlsl with M = Mn, Fe, Co, Ni, and Zn were obtained by the same group (77, 78). All these compounds, except the last one, exhibit a three-dimensional magnetic ordering. The critical temperatures were found to be 6 K for M = Mn, 12 K for M = Fe, 10 K for M = Co, and 14 K for M = Ni. Below, the compounds behave as soft magnets with rather weak coercive fields. The largest coercitivity was found for the Fe(II)Cr(III) derivative the coercive field at 5 K is reported as 320 Oe. 

The FMR turns out to be weakly sensitive to the onset of the teeth in the energy density profile. As it was noticed above, the saturating magnetic field eliminates quasi ultrametricity, i.e. the teeth in the energy profile. Formally this is accomplished by the dependence of parameters a, B and C on Therefore the experimental and theoretical investigations of temperature-driven correlations in the coercitivity of blocked state of superparamagnefic particle ensemble revealed the crossover from SPM to SSG state and subsequently to SFM state at temperature decreasing. 

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