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Chapter 20: Problem 27

Briefly explain the manner in which information is stored magnetically.

Short Answer

Expert verified
Answer: Magnetic data storage works by using magnetic domains within certain materials to store binary information. This is achieved by applying an external magnetic field to a storage medium using a write head, causing the magnetic domains to align according to the field's direction and represent a binary value (0 or 1). To read the stored information, a read head moves over the storage medium and detects the magnetic fields created by the aligned magnetic domains, which are then converted into electrical signals and interpreted as binary data.

Step by step solution

01

Understand magnetic domains

Magnetically stored information relies on the behavior of magnetic domains within certain materials. Magnetic domains are microscopic regions in a magnetic material, like a ferromagnet, where the spins of electrons are aligned in the same direction. This alignment creates a local magnetic field which can be manipulated to store data.
02

Explain the storage medium

The storage medium is typically a thin film made of magnetic materials such as iron, nickel, or cobalt, which is deposited on a non-magnetic substrate. This medium is composed of tiny magnetic grains or particles which are capable of holding a magnetic field when exposed to an external field. Each grain represents a single magnetic domain and can store one bit of information.
03

Describe the writing process

Information is stored magnetically by applying an external magnetic field to the storage medium. This external field is usually applied using a write head, which is an electromagnet capable of producing a strong localized magnetic field for a short period of time. When the write head applies a magnetic field to a specific area of the storage medium, the magnetic domains in the affected area align according to the applied field's direction. This alignment represents a binary value - either a 0 or a 1.
04

Discuss the reading process

In order to read the stored information, a read head is used, which is typically a sensitive magnetoresistive or inductive sensor. As the read head moves over the storage medium, it detects the magnetic fields created by the aligned magnetic domains. These detected signals are then converted into electrical signals, which are further processed and interpreted as binary data.
05

Summary

In summary, magnetic data storage relies on the principles of magnetism, using magnetic domains to store binary information. The process involves writing data by applying an external magnetic field to a storage medium, causing the magnetic domains to align according to the applied field's direction. The stored information is then retrieved by a read head, which detects the magnetic fields created by the aligned magnetic domains and converts them into electrical signals for further processing.

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Most popular questions from this chapter

(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?

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

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.

An iron bar magnet having a coercivity of \(7000 \mathrm{A} / \mathrm{m}\) is to be demagnetized. If the bar is inserted within a cylindrical wire coil \(0.25 \mathrm{m}\) long and having 150 turns, what electric current is required to generate the necessary magnetic field?

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.
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