浙江大学物理学在高新材料中应用.ppt

The Nobel Prize in Physics 2007 - for the discovery of Giant Magnetoresistance Atomic orbital magnetic dipole moment Atomic dipole → tiny current loop μB is Bohr magneton 1. Paramagnetism The atoms of this material have permanent magnetic dipole moments. B0 and μ0M are parallel, B B0. ?m 1 Curie’s law: when B0/T is small Adiabatic demagnetization to decrease the temperature of system. 铁磁性元素: Fe, Co, Ni, 及合金 Why formed domains Atomic structure and electron-spin More…? 铁磁性元素: Fe, Co, Ni, 及合金 磁性掺杂元素： Ti、V、Cr、Mn、Fe、Co、。。。 空穴/电子掺杂元素： Li、Na、K / F、Cl、Br 。。。 ? H = H 0 + J pd S S I · s i ? holes Mn spins 硬盘中的磁介质结构 基片 介底层 过度层 磁性层 保护层 润滑层 多层的金属薄膜结构 特性之一：具备记录功能的磁特性 特性之二：具备耐久的机械润滑功能 特性之三：亞于钠米的超表面光洁度 反铁磁耦合的磁介质 反铁磁耦合的磁介质增强热稳定性 常规的磁介质 反铁磁耦合的磁介质 Mrt ~ Mrt1 – Mrt2 KUVeff ? KUVupper layer ? E Abarra et al, Appl. Phys. Lett. Vol.77, 2581, 2000 ? E. Fullerton et al, Appl. Phys. Lett. Vol.77 3806, 2000 记录的模式之一：纵向磁记录 　最经典的读写方式 　技术成熟 　造价较低 　面临高密度极限的挑战 硬盘中的读写磁头结构 该项技术的关键是开发出了在多层膜的上下，设置有两层用以 增强灵敏度的极薄的氧化物层的 双镜面型GMR磁头 Which physics law in the磁头? Faraday-Whilst was attempting to explain a discovery to either Gladstone (Chancellor) or Peel (Prime Minister) he was asked, “But, after all, what use is it?” Faraday replied, “Why sir, there is the probability that you will soon be able to tax it.” Faraday’s law of induction 磁感应的应用-金属检查通道 磁感应的应用-无线充电器 电吉他工作原理 Which physics law in the 磁头? 磁阻现象（Magnetic Resistance） Ohm’s Law: A Microscopic View (电阻的物理图像） Illustration of electrons’ drift The drift speed vd The electron acceleration acquired in the applied electric field is, As a result, during the time-interval τ between two one-after-another collisions, the electron’s speed changes from zero into: T: temperature of the conductor λ: mean free path of electrons On an average sense, the electrons’ drift velocity is defined as above vf: The Conductivity The direction of the curren