mse20 - Chapter 20: Magnetic Properties ISSUES TO ADDRESS....

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1 Chapter 20 - 1 ISSUES TO ADDRESS. .. • How do we measure magnetic properties? • What are the atomic reasons for magnetism? • Materials design for magnetic storage. • How are magnetic materials classified? Chapter 20: Magnetic Properties • What is the importance of superconducting magnets? Chapter 20 - 2 • Created by current through a coil: • Relation for the applied magnetic field, H : L I N H = applied magnetic field units = (ampere-turns/m) current Applied Magnetic Field Applied magnetic field H current I N = total number of turns L = length of each turn
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2 Chapter 20 - 3 • Magnetic induction results in the material • Magnetic susceptibility, χ (dimensionless) Response to a Magnetic Field current I B = Magnetic Induction (tesla) inside the material χ measures the material response relative to a vacuum. H B vacuum χ = 0 χ > 0 χ < 0 Chapter 20 - 4 • Measures the response of electrons to a magnetic field. • Electrons produce magnetic moments: • Net magnetic moment: --sum of moments from all electrons. • Three types of response. .. Magnetic Susceptibility Adapted from Fig. 20.4, Callister 7e . magnetic moments electron nucleus electron spin
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3 Chapter 20 - 5 Plot adapted from Fig. 20.6, Callister 7e . Values and materials from Table 20.2 and discussion in Section 20.4, Callister 7e . 3 Types of Magnetism Magnetic induction B (tesla) Strength of applied magnetic field ( H ) (ampere-turns/m) vacuum ( χ = 0) -5 diamagnetic ( χ ~ -10 ) (1) e.g., Al 2 O 3 , Cu, Au, Si, Ag, Zn ferromagnetic e.g. Fe 3 O 4 , NiFe 2 O 4 ferrimagnetic e.g. ferrite( α ), Co, Ni, Gd
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This note was uploaded on 03/18/2010 for the course ME 2580 taught by Professor Vandenbrink during the Spring '08 term at Western Michigan.

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mse20 - Chapter 20: Magnetic Properties ISSUES TO ADDRESS....

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