Ferrimagnetism hysteresis loops

Whether a phase displays SD, PSD orMD behaviour, can be determined from the shape of its hysteresis loop. In MD particles the Bloch walls can be moved by lower energies than the directions of magnetization in SD particles. The hysteresis loops of MD particles, therefore, are much narrower than those of SD particles (Fig. 7.12). For ferrimagnetic phases, the ratios Jrs/Js and Har/Hc (Fig. 7.9) (Day et al., 1977) can be used to distinguish between SD, PSD, and MD particles (Fig. 7.12, right). It should be kept in mind, however, that the coercive forces also depend on particle morphology. Calculations by Butler and Banerjee (1975) show that deviations from the rounded isometric shape towards elongated needles stabilize the SD behaviour and even SP particles may become SD (Fig. 7.13). 

The resulting crystals are dark red and are partly of a pseudohexagonal habit as indicated by b/a being close to The dimensions of the orthorhombic cell at room temperature are a = 7.433, b= 12.875, c= 13.730 A.6 Below Curie temperature Tc = 3.5 K the compound transforms to a ferrimagnet exhibiting a distinct hysteresis loop and a marked anisotropy. The Sm salt is fairly stable in air. With acids poisonous HCN gas is evolved. 

According to Figure 15.11(a), the hysteresis curve for ferrite nanopowders at room temperature showed that the particles are ferrimagnetic above the blocking temperature of 50 The hysteresis loop parameters, like saturation magnetization (Ms), coercivity field Hq), magnetic remanence (Mr) and an... 

Concept Check 20.6 It is possible, by various means (e.g., alteration of microstructure and impurity additions), to control the ease with which domain walls move as the magnetic field is changed for ferromagnetic and ferrimagnetic materials. Sketch a schematic B-versus-H hysteresis loop for a ferromagnetic material, and superimpose on this plot the loop alterations that would occur if domain boundary movement were hindered. 

There is technical interest in ferrimagnetics. The majority of than are antiferromagnetics, the structure of which includes two (or more) ions whose magnetic moments differ, and therefore sublattices do not completely compensate each otha in the crystal. The macroscopic magnetic moment arises. In many respects, a ferrimagnetic crystal behaves as a ferromagnetic one. The domain structure and, consequently, a hysteresis loop, also exhibit. 

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