Bloch walls

Blister or strip packs Blister packaging Bloch walls Block copolymers... 

The application of higher fields to a sample gradually moves the Bloch walls or changes the directions of magnetization until a maximum magnetization is reached. 

In multidomain particles each domain is separated from another by the Bloch wall, where... 

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). 

For technical applications (sensors), Hristoforou et al. (1998) have developed an interesting method to determine the field-dependence of the magnetostrictive strain, based on measuring the delay due to Bloch-wall motion. 

Bloch walls - [MAGNETIC MATERIALS - THIN FILMS AND PARTICLES] (Vol 15)... 

An important property of a Bloch wall is its mobility. It can be seen from Fig. 9.9 that the application of H in the sense shown will cause the wall to move to the left by a series of minor rotations of the vectors. A more detailed consideration of wall displacements shows them to be of two types, reversible or irreversible which one occurs depends upon the size of the displacement and the... 

Fig. 9.9 The change in spin orientation across the width of a Bloch wall.

There is another, quite distinct, resonance phenomenon concerned with domain wall movements occurring at approximately one-tenth of the ferrimagnetic resonance frequency. To understand this Bloch wall motion needs to be... 

Figure 3.30. Representation of a Bloch wall expansion resulting from an applied magnetic field impinging on a ferromagnetic material.

A ferromagnetic material consists of magnetically ordered domains separated by transition zones, the so-called Bloch walls (ca 30 nm). In finely divided ferromagnetic compounds, with size less than this critical value, particles consist of magnetic sing. e domains, At temperature T, they may exhibit a kind of Brownian movement, affecting the orientation of the magnetic moment p of the particle considered as a whole (p = Npo N,... 

Broz JS, Braun HB, Brodbeck O, Baltenspeiger W, Helman JS (1990) Nncleation of magnetization reversal via creation of pairs of Bloch walls. Phys Rev Lett 65 787-789 Brag JA, Anthony TC, Nickel JH (1996) Magnetic recording head materials. Mater Res Soc Bnll, September 1996 23-27... 

Our attention is focused on the properties of periodic trains formed by kinks or traveling Bloch walls. Our analysis reveals that, depending on the parameters of the oscillatory medium and the spatial period of a train, it can undergo a reversal of its propagation direction [19]. We show how this phenomenon can be used to design traps for traveling kinks and Bloch walls. Furthermore, we find that a new kind of patterns - twisted rotated spiral waves - exist in oscillatory media under the conditions of front propagation reversal. 

The above analysis shows that front propagation reversal occurs near any n 1 resonance. For ji = I, stationary kinks (i.e., 27r-froiits) and periodic sequences of standing kinks are possible (the existence of stationary solitary kinks under global feedback conditions has previously been shown [15]). For 71 = 1, stationary tt-fronts represent standing Bloch walls or their periodic secjuences. Such standing structures are oscillation amplitude does not vanish here. 

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