Classifications of magnetic materials Diamagnets  =-10-5 ex) Cu, silver, gold bismuth, beryllium, superconductor (=-1) Paramagnets  =10-3 ~10-5  The magnetization of paramagnets is weak but aligned parallel with direction of the magnetic field ex) Al, Platinum, Mn 3. Ferromagnets  >1 (cf.  50 to 10000) ex) Fe, Co, Ni, Sm, Dy, Tb

자기감수율(magnetic susceptibility) & 상대투자율(relative permeability) Bm:물질 내부유도 자기장

Values of    for various materials    constant in dia, paramagets    are strongly affected by H  T in ferro Dia, para, ferro Other materials are all very closely related to ferromagnets because they are magnetically ordered ex) ferrimmgnets, antiferromagnets, helimagnets  superparamagnets

Magnetic Properties of Ferromagets Ferromagnetism-Basic Properties Spontaneous magnetization Ms(T) below Tc T   Ms(T)  : T  TC  MS (T)  0 Magnetic properties reproducible on heating above TC, provided no structural change during heating No macroscopically observable apparent (net) magnetization at zero field Net magnetization by applied magnetic field

Ferromagnetism-Domains Spontaneously magnetized regions separated by domain walls 180º domain walls: 90º domain walls Domain size determination by energy balance between magnetostatic energy and domain wall energy 

Ferromagnetism-Hysteresis Loops Magnetization process: domain wall motion and spin rotation Remanent magnetization, remanence ratio, coercive force coercivity) Coercivity(strongly structure-sensitive) varies)