Chapter 14 Magnetic Fields: VII a Magnetization M The equivalent Surface Current Density The equivalent Volume Current Denisity J Calculation of Magnetic Fields in Material Magnetic Field intensity H Ampere' s circuit Law Magnetic Susceptibility, permeability a Magnetization Curve a Hysterisis
Chapter 14 Magnetic Fields:VII ◼ Magnetization M ◼ The Equivalent Surface Current Density ◼ The Equivalent Volume Current Denisity J ◼ Calculation of Magnetic Fields in Material ◼ Magnetic Field Intensity H ◼ Ampere’s Circuit Law ◼ Magnetic Susceptibility, Permeability ◼ Magnetization Curve ◼ Hysterisis
14. 1 Magnetization M So far we have studied only those magnetic fields ue to tree charges. In fact, all bodies contain spinning electrons moving in orbits, and they also produce magnetic fields Magnetized: Magnetic materials are similar to di- electrICs, Charges can possess magnetic moments, and these together can produce a resultant magnetic moment in a macroscopic body. Such a body is said to be magnetized
n most atoms the magnetic moments associated with the orbital and spinning motions of electrons cancel Paramagnetic: If the cancellation is not complete the material is said to paramagnetic When such a substance is put into a magnetic field gmeD→mm0mm010m Diamagnetic: in diamagnetic materials the elemen tary magnetic moments are not permanent but are nduced
erromagnetIC: in ferromagnetic materialS, such as iron, the magnetization can be much larger than that ot para-or diamagnetIc substances Domain: in ferromagnetic materials there are re gions in which electron spins are aligned. The mag netization of one domain may be oriented at random w.r.t. that of a neighboring domain Remark: usually dielectric D O E, linear; but in ferromagnetic materials the magnetization is non linear and depends on history
14.1 The Magnetization The magnetization M is the magnetization moment per unit volume at a given point If m is the average magnetic dipole moment per atom and they are aligned in the same direction, then the magnetization M=Nm where N is the number density of atoms M has unit: ampere/meter