91Ó°ÊÓ

(a) Explain the two sources of magnetic moments for electrons. (b) Do all electrons have a net magnetic moment? Why or why not? (c) Do all atoms have a net magnetic moment? Why or why not?

The magnetic flux density within a bar of some material is 0.630 tesla at an \(H\) field of \(5 \times 10^{5} \mathrm{A} / \mathrm{m} .\) Compute the following for this material: (a) the magnetic permeability, and (b) the magnetic susceptibility. (c) What type(s) of magnetism would you suggest is(are) being displayed by this material? Why?

The magnetization within a bar of some metal alloy is \(1.2 \times 10^{6} \mathrm{A} / \mathrm{m}\) at an \(\mathrm{H}\) field of \(200 \mathrm{A} / \mathrm{m} .\) Compute the following: (a) the magnetic susceptibility, (b) the permeability, and (c) the magnetic flux density within this material. (d) What type(s) of magnetism would you suggest as being displayed by this material? Why?

Compute (a) the saturation magnetization and (b) the saturation flux density for iron, which has a net magnetic moment per atom of 2.2 Bohr magnetons and a density of \(7.87 \mathrm{g} / \mathrm{cm}^{3}\).

The formula for samarium iron garnet \(\left(\mathrm{Sm}_{3} \mathrm{Fe}_{5} \mathrm{O}_{12}\right)\) may be written in the form \(\mathrm{Sm}_{3}^{c} \mathrm{Fe}_{2}^{a} \mathrm{Fe}_{3}^{d} \mathrm{O}_{12},\) where the superscripts \(a, c\) and \(d\) represent different sites on which the \(\mathrm{Sm}^{3+}\) and \(\mathrm{Fe}^{3+}\) ions are located. The spin magnetic moments for the \(\mathrm{Sm}^{3+}\) and \(\mathrm{Fe}^{3}\) ions positioned in the \(a\) and \(c\) sites are oriented parallel to one another and antiparallel to the \(\mathrm{Fe}^{3+}\) ions in \(d\) sites. Compute the number of Bohr magnetons associated with each \(\mathrm{Sm}^{3+}\) ion, given the following information: (1) each unit cell consists of eight for mula \(\left(\mathrm{Sm}_{3} \mathrm{Fe}_{5} \mathrm{O}_{12}\right)\) units; (2) the unit cell is cubic with an edge length of \(1.2529 \mathrm{nm}\) (3) the saturation magnetization for this material is \(1.35 \times 10^{5} \mathrm{A} / \mathrm{m} ;\) and (4) assume that there are 5 Bohr magnetons associated with each \(\mathrm{Fe}^{3+}\) ion.

Briefly explain why the magnitude of the saturation magnetization decreases with increasing temperature for ferromagnetic materials, and why ferromagnetic behavior ceases above the Curie temperature.

Briefly describe the phenomenon of magnetic hysteresis, and why it occurs for ferromagnetic and ferrimagnetic materials.

Cite the differences between hard and soft magnetic materials in terms of both hysteresis behavior and typical applications.

Briefly explain the manner in which information is stored magnetically.

Cite the differences between type I and type II superconductors.