自旋电子学系列讲座自旋电子学系列讲座(4)自旋转移力矩自旋转移力矩 翟亚翟亚巨磁电阻效应 (GMR)是磁性多层膜的电阻值随外加磁场而发生巨大变化的行为！有没有逆效应呢？自旋角动量转移效应 (简称STT效应)1996年，Slonczewski 和 Berger 通过理论计算预测出，当自旋极化电流流过纳米尺寸的铁磁薄膜或金属磁性多层膜中时，极化电流与多层膜中的散射会带来由极化电子到铁磁薄膜磁矩的自旋角动量转移，从而对铁磁薄膜磁矩产生自旋矩，引起铁磁薄膜磁矩的不平衡，使之发生转动，进动甚至使磁化方向翻转运用极化电流改变磁性膜的磁化方向的概念，很可能为我们提供了一种崭新概念的“电流驱动”纳米器件，即采用电流直接穿过元件，而不是利用电流导线产生的环形磁场来改变磁性纪录元件的记忆信号关于Spin transfer torque 的文章：?Physical Review B and Physical Review Letters: >120篇?Nature all other features are artifacts of the fabrication process. The directions of rotating field components (Hx and Hy ), and the sense of field rotation (Rot) are indicated, and the asterisk denotes the position of MOKE measurement. (B) Schematic diagram with arrows illustrating the route of a domain wall propagating through the magnetic structure within a counterclockwise rotating field. (C) MOKE trace obtained from the position marked with an asterisk of the nanowire structure within an applied counterclockwise rotating field with amplitudes Hx 0 = Hy 0 = 91 Oe.SCIENCE, 309 1690 (2005) (A) FIB image of a magnetic nanowire network containing one NOT gate, one AND gate, two fan-out junctions, and one cross-over junction. MOKE measurements were made at positions I and IV, indicated by asterisks, and positions II and III denote the inputs to the AND gate. Also indicated are the directions of field components (Hx and Hy) and the sense of field rotation (Rot). (B) MOKE traces describing the operation of the magnetic circuit within a counterclockwise rotating field with amplitudes Hx0 075 Oe and Hy0 0 88 Oe and dc offset of Hx DC 0 –5 Oe. Experimental MOKE measurements from positions I and IV of the circuit are shown. Traces II and III are inferred from trace I and show the magnetization state of the AND gate’s input wires.Symbols for electronic logic, together with the appropriate CMOS circuit element and a schematic drawing of the optimized domain-wall logic element (dimensions shown refer to the design rule used here of 200-nm–wire width connecting logic elements and 1-mm turning radius of corners). The fan-out, cross-over, and logical AND junctions all contain tapered regions to connect to the 200-nm-wide wire links. Vdd is the supply voltage.Domain wall memoryCourtesy of Stuart ParkinMagnetic race-track memoryA novel three-dimensional spintronic storage class memory The capacity of a hard disk drive but the reliability and performance of solid state memory - a disruptive technology based on recent developments in spintronic materials and physicse. Current induced domain wall displacement (i) Constriction in nanowire (Xu YB)Micromagnetic simulations for necked NiFe wires with constriction widths of (a) 50 nm, (b) 100 nm, (c) 250 nm, and (d) 300 nm.纳米线宽度对畴壁形成的影响半锥角对纳米接触处磁矩分布的影响36度27度14度10度7度Ni材料对纳米接触处磁矩分布的影响材料出现畴壁的范围Ni27-7度Py10-7度Fe14-10度Co14-10度Thank you for attention。