Chapter 20: Problem 10
There is associated with each atom in paramagnetic and ferromagnetic materials a net magnetic moment. Explain why ferromagnetic materials can be permanently magnetized whereas paramagnetic ones cannot.
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Chapter 20: Problem 10
There is associated with each atom in paramagnetic and ferromagnetic materials a net magnetic moment. Explain why ferromagnetic materials can be permanently magnetized whereas paramagnetic ones cannot.
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Estimate saturation values of \(H\) for singlecrystal iron in [100], [110], and [111] directions.
It is possible to express the magnetic susceptibility \(\chi_{m}\) in several different units. For the discussion of this chapter, \(\chi_{m}\) was used to designate the volume susceptibility in SI units, that is, the quantity that gives the magnetization per unit volume \(\left(\mathrm{m}^{3}\right)\) of material when multiplied by \(H\). The mass susceptibility \(\chi_{m}(\mathrm{~kg})\) yields the magnetic moment (or magnetization) per kilogram of material when multiplied by \(H ;\) similarly, the atomic susceptibility \(\chi_{m}\) (a) gives the magnetization per kilogram-mole. The latter two quantities are related to \(\chi_{m}\) through the relationships $$ \begin{aligned} &\chi_{m}=\chi_{m}(\mathrm{~kg}) \times \text { mass density (in } \mathrm{kg} / \mathrm{m}^{3} \text { ) } \\ &\left.\chi_{m}(\mathrm{a})=\chi_{m}(\mathrm{~kg}) \times \text { atomic weight (in } \mathrm{kg}\right) \end{aligned} $$ When using the cgs-emu system, comparable parameters exist, which may be designated by \(\chi_{m}^{\prime}, \chi_{m}^{\prime}(\mathrm{g})\), and \(\chi_{m}^{\prime}(\mathrm{a})\); the \(\chi_{m}\) and \(\chi_{m}^{\prime}\) are related in accordance with Table 20.1. From Table \(20.2, \chi_{m}\) for silver is \(-2.38 \times 10^{-5}\); convert this value into the other five susceptibilities
The following data are for a transformer steel: \begin{tabular}{cccc} \hline \multicolumn{3}{c}{\(\boldsymbol{B}\)} \\ \(\boldsymbol{H}(\mathrm{A} / \mathrm{m})\) & \((\) teslas \()\) & \(\boldsymbol{H}(\mathbf{A} / \mathrm{m})\) & \(\boldsymbol{B}\) (teslas) \\ \hline 0 & 0 & 200 & \(1.04\) \\ 10 & \(0.03\) & 400 & \(1.28\) \\ 20 & \(0.07\) & 600 & \(1.36\) \\ 50 & \(0.23\) & 800 & \(1.39\) \\ 100 & \(0.70\) & 1000 & \(1.41\) \\ 150 & \(0.92\) & & \\ \hline \end{tabular} (a) Construct a graph of \(B\) versus \(H\). (b) What are the values of the initial permeability and initial relative permeability? (c) What is the value of the maximum permeability? (d) At about what \(H\) field does this maximum permeability occur? (e) To what magnetic susceptibility does this maximum permeability correspond?
Briefly describe the phenomenon of magnetic hysteresis, and why it occurs for ferromagnetic and ferrimagnetic materials.
Assume there exists some hypothetical metal that exhibits ferromagnetic behavior and that has (1) a simple cubic crystal structure (Figure \(3.24\) ), (2) an atomic radius of \(0.153 \mathrm{~nm}\), and (3) a saturation flux density of \(0.76\) tesla. Determine the number of Bohr magnetons per atom for this material.
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