B-H curve

Figure 28.28 A typical magnetic saturation (B-H) curve for CRGO sheets...

To determine the value of p, the saturation or the B-H curve of the silicon steel being used must be available. Assuming a normal flux density for such a core to be 1 1 wb/ m (see also Section 1.9) and making use of a normal B-H curve as shown in Figure 28.28, the corresponding value of H for a value of B as 1.1 wb/m can be read as 200 A/m,... 

Transparency. Transparency is expressed quantitatively as the transparency number. This is defined as the reciprocal of the increase in color difference AE b on a black substrate obtained on increasing the film thickness h of the pigmented medium. The transparency number has the unit mm ( = L/m2). It indicates the number of liters of pigmented medium needed to coat 1 m2 of a black substrate in order to obtain a color difference of AE%b = 1 relative to this substrate. In a simplified method the transparency number can be determined by evaluating one or two points on the straight part of the AE b(h) curve. A computer method is more exact, furthermore calculations can be made using the spectral principle of spectral evaluation (see above). For standards, see Table 1 ( Transparency ). 

Each of the ferromagnetic materials has a specific crystallographic direction in which it is naturally magnetized. Figure 18.9 shows the B-H curves for iron... 

B-H curves for several directions in iron. After J. K. Stanley, Electrical and Magnetic Properties of Metals (Materials Park, OH ASM, 1963). Reprinted with permission of ASM International. All rights reserved. www.asminternational.org. 

If the field is removed, there is a residual magnetization or remanence, Br. A reverse field, //, (coercive force), is required to demagnetize the material. The area enclosed by the B-H curve (hysteresis) is the energy loss per cycle, and the... 

A high //, coercive force is desirable for hard magnets, but most important is a high H x B product. The second quadrant of the B-H curve (Figure 18.23) is most important. Often the maximum B x H product (Figure 18.24) is taken as a figure of merit. 

Second quadrant of B-H curves for selected alloys. From R. M. Rose, L.A. Shepard, and J. Wulff, The Structure and Properties of Materials, vol. IV, Electronic Properties (New York Wiley, 1996). Reprinted with permission of John Wiley Sons, Inc. 

Figure 17. (A) Typical hysteresis loop of a FePt-Fe3Pt nanocomposites and (B) Second-quadrant B-H curves for the annealed 4 nm Fe58Pt42 nanoparticle assembly and hard-soft exchange-coupled FePt-Fe3Pt nanocomposite [75].

Fig. 35. Comparision of the hard magnetic properties of two hard magnetic materials a and b. (Left) Flux density B (full lines) and magnetic polarization J (dashed lines) as a function of the demagnetizing field strength H. (Right) Product BH (horizontal axis) plotted versus B (vertical axis) for both materials a and b. The working point corresponding to (BFf)max is indicated on the B(H) curve (left point for material a and b) by a filled and open circle, respectively.

Fig. 36. Comparison of the B(H) curves of rare earth-base materials having a large intrinsic magneto-crystalline anisotropy with the B(H) curve of Ticonal XX in which the magnetic hardness originates...

Figure 4 a. B-H curve of Fc304 prepared by hydrothermal method b. B-H curve of Fe304 prepared... 

B = 0). The initial slope of the B-H curve is called the initial magnetic permeability and... 

The ferroelectric effect was discovered in 1920 by Valasek, who obtained hysteresis curves for Rochelle salt analogous to the B-H curves of ferromagnetism [5.5], and studied the electric hysteresis and piezoelectric response of the crystal in some detail [5.6]. For about 15 years thereafter, ferroelectricity was considered as a very specific property of Rochelle salt, until Busch and Scherrer discovered ferroelectricity in KH2PO4 and its sister crystals in 1935. During World War II, the anomalous dielectric properties of BaTiOs were discovered in ceramic specimens independently by Wainer and Solomon in the USA in 1942, by Ogawa in Japan in 1944, and by Wul and Goldman in Russia in 1946. Since then, many ferroelectrics have been discovered and research activity has rapidly increased. In recent decades, active studies have been made on ferroelectric liquid crystals and high polymers, after ferroelectricity had been considered as a characteristic property of solids for more than 50 years. 

Fig. 1. Nuclear potential energy curves for the parrallel sequential-superexchange mechanism. The super-exchange unistep occurs by the activationless crossing from the P BH curve (solid line) to the P+BH" curve (dashed line), while the first step (k ) in the two-step sequential process occurs (in the classical limit) by thermal activation on the P BH curve to its crossing with the P+B"H curve (dash-dotted line) followed by curve crossing. AG and AG are the free energy gaps between P bh and P+BH" and between P BH and P B H, respectively, while 5E is the vertical energy difference.

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