磁性材料简介磁性材料的种类以及其形成机制s_api.ppt

? FERROMAGNETIC DOMAINS ? FERROMAGNETIC DOMAINS The directions of magnetization of different domains need not be parallel. An arrangement of domains is tend to approximately zero resultant magnetic moment. Domains form also in antiferromagnetics, ferroelectrics, anti-ferroelectrics, and superconductors etc. * ? SINGLE DOMAIN PARTICLES ? SINGLE DOMAIN PARTICLES * ? SINGLE DOMAIN PARTICLES MFM Magnetic Force Microscope AFM Atomic Force Microscope SiN tip STM Scanning Tunneling Microscope W/Pt tip SPM Surface Probe Microscope * ? SINGLE DOMAIN PARTICLES * 磁阻測量、居理溫度測量實驗 * 磁阻效應 磁阻 ??(H) 是被定義為樣品在磁場中電阻之改變量，即??(H) = ?(H) - ?(H = 0)，此處 ?(H) 是在磁場H 下樣品之電阻率。 材料有不同之磁阻,其原因可來自; 電荷受羅倫茲力之作用而改變甚行進路徑造成電荷與晶格間散射機率增加, 此時 ??(H) 0 ; 受磁矩在磁場下電子自旋與磁矩間間散射狀態改變的影響, 若樣品是鐵磁性材料, 其磁矩對電荷自旋之散射機率會因為外加磁場之增加而減小, 此時 ??(H) 0 。 其他物理原因。 * X Z Y A B H J X Z H Y J (a) (b) A B 樣品置於外加磁場H 之中, 若將電流 J 通於樣品, 此樣品在磁場下產生磁阻效應。(a)為縱向磁阻效應 (H 之方向平行於J之方向);(b)為橫向磁阻效應(H之方向垂直於J之方向) * Nd,Sr Mn O b (5.46 ?) c (7.7 ?) a (5.47 ?) 氧化物 Nd1-XSrXMnO3 巨磁阻材料中Nd, Sr, Mn 和O原子之排列情形， 此化合物之居禮溫度約在 230 K。 * NSMO and LCMO films show the Curie temperature at 222 K and 250 K respectively. * ● The pattern for resistivity and Hall measurements V = V3-V2→Resistance Vh = V2-V1→Hall coefficient * Temperature dependence of the longitudinal resistivity ?xx for YBa2Cu3Oy (YBCO) (1500 ? and NSMO (2100 ?) films. (b) * Nd1-XSrXMnO3薄膜在 (a)不同磁場下電阻與溫度的相依行為; (b)磁阻比與溫度的相依行為 * 巨磁阻Pr0.7Sr0.3MnO3薄膜在溫度為30 K的電阻對角度?B相依行為，?B為磁場與基座法線之夾角。由上而下的圖形外加磁場值分別為600 G，2500 G，4500 G，5500 G，12.5 kG，20 kG 及 60 kG。 * Diamagnetism Paramagnetism Ferromagnetism Antiferromagnetism Others 磁性 * Diamagnetism Diamagnetism is a form of magnetism which is only exhibited by a substance in the presence of an externally applied magnetic field. It is the result of changes in the orbital motion of electrons due to the application of an externally applied magnetic field. Applying a magnetic field creates a magnetic force on a moving electron in the form of F=qv x