材料物理性能Physics properties of____ material.ppt

原因：有退磁场产生。 退磁场Hd大小： 和材料的磁化强度M，材料的形状成正比：?Hd=－NM 退磁场产生的能量称退磁能 对x方向的细长针形： X θ 对于薄板(xy面)，退磁场系数：Nz=1 ,Nx=Ny=0 ?=0 ,垂直x-y面，能量最高；? =?/2 ,平行x-y面时能量最低。因而面内磁化是最容易的方向。如果Is比较小时，垂直和面内退磁能的差也比较小。 θ （7）磁畴 铁磁性材料的主要特点是具有磁畴结构。 顺磁材料， 铁磁材料 磁畴形成的原因是为了降低退磁能。 A b c d Physics properties of material Magnetic propertiesDielectric properties Magnetic behaviors(14h) 1 Definitions and General Relations 2Types of Magnetism 3 Basic magnetic properties 4 技术磁化 5 永磁性 6 动态磁化 7 巨磁阻 Dielectrics (8h) 1 Definitions and General Relations 2 Mechanisms of Polarization 3 Frequency Dependence of the Dielectric Constant 4. Dynamic Properties 5. Ferro Electricity 6.Piezo Electricity and Related Effects Magnetic behaviors What is magnetism? You have been observing a property of matter called magnetism. Magnetism is the force of attraction or repulsion in a material. Certain materials such as iron, steel, nickel, or magnetite exhibit this force while most other materials do not. 1 Definitions and General Relations（1)Fields, magnetic induction and Permeability Biot-savart law: dl is the length of a conductor; n is a unit vector along the radial direction. Magnetic fields are produced by electric currents, which can be macroscopic currents in wires, or microscopic currents associated with electrons in atomic orbits. 磁矩?m=iA The first basic relation that we need is the relation between the magnetic flux density (magnetic induction), B and the magnetic field strength H in vacuum. B?=μo · H If a magnetic material is present, the relation between magnetic field strength and magnetic flux density becomes B? =μo(H+M)=μH μ: magnetic permeability [B] = Vs/m2, with 1Vs/m2 = 1 Tesla H = magnetic field strength , [H] = A/m μ: permeability of the material μo = magnetic permeability of the vacuum = 4? · 10–7 Vs/Am Example1: Fulx differences between air and