Lec17 - Lecture 17 Lecture 17-1 Magnetization and...

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Unformatted text preview: Lecture 17 Lecture 17-1 Magnetization and “Bound”Current in Matter Magnetization M V μ = ca cca d M dV μ = ca cca d Adidi M Adl Adldl μ ∴ = = = current /length Equivalent to a solenoid of nI=M m nI B M μ μ ∴ = = Lecture 17 Lecture 17-2 Magnetism Exhibited by Materials • Diamagnetism: (small) magnetic moment opposite to the external magnetic field B app is induced • Paramagnetism: magnetic moment of individual atoms become aligned parallel to the applied magnetic field B app U B μ =− caca i repelled from region of large B attracted toward region of large B • Ferromagnetism: magnetic moment of individual atoms are already (partially) aligned in some direction even if B app =0 Any material –but shows only if non- paramagnetic transition element, rare earth, ... Fe, Ni,... • Antiferromagnetism: like ferromagnetism except that alternating moments are (partially) aligned opposite to each other (when B=0) Mn, Cr,... Lecture 17 Lecture 17-3 Hysteresisfor a Ferromagnet Lack of retraceabilityshown is called hysteresis . h Memory in magnetic disk and tape h Alignment of magnetic domains...
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This note was uploaded on 04/07/2008 for the course PHYS 241 taught by Professor Wei during the Spring '08 term at Purdue.

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Lec17 - Lecture 17 Lecture 17-1 Magnetization and...

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