材料性能 Ch5_Magnetic Properties of Materials.ppt

§5-1 Fundamentals of Magnetism in Solids 2. Magnetic induction, or Magnetic flux density B/磁感应强度(磁流密度) maximum permeabilityμdetermination §5-2 Magnetization of materials Origin of magnetism in Solids Atom or molecules magnetic moment! Completely filled： there is total cancellation of both orbital and spin moments Partially filled : net atom magnetic moment! Example: Fe, 3d64s2 ,4 electrons magnetic moments. Materials are affected in different way by a magnetic field §5-3 Diamagnetism and Paramagnetism 材料抗磁性和顺磁性 Paramagnetism/材料顺磁性 Dependence on sub-atomic structure Electron orbital motion ：diamagnesium Permant magnetic dipole：paramagnesium Free electrons：diamagnesium paramagnesium Ferromagnetism/铁磁性(－ Magnetic materials/磁性材料) Causes of ferromagnesium * 结束放映 下一页 上一页 Materials Properties MP,SWJTU Prof. Guojinag Wan Chap 5. Magnetic Properties of Materials 材料的磁学性能 6 Magnesia Magnetism The first magnetic phenomenon observed were those associated with naturally occurring magnets, fragments of iron ore found near the ancient city of Magnesia, Turkey (hence the term magnet) Magnetic field lines of force around a current loop and a bar magnet 1. Magnetic field strength H /磁场强度 Magnetic forces are generated by moving electrically charged particles . Origin of magnetic force: all magnetic phenomena result from the forces between electrical charges in motion. That is, charges in motion set up a magnetic field as well as an electrical field, and this magnetic field exerts a force on other charges in the vicinity. Namely, a moving charge creates a magnetic field in the space around it, and the magnetic field exerts a force on other moving charges in the field. In vacuum For materials， Permeability μ/磁导率:a measure of the degree to which the material can be magnetized, or the ease with which a B field can be induced in the presence of an external H field. Magnetic induction or Magnetic flux density B ：magnitude of the internal field strength wi