Magnetic Tunnel Junctions with MgO／Al-O Composite Barriers

Magnetic tunnel junctions (MTJs) with structures of Ta(5 nm)/Cu(30nm)/Ta(5 nm)/Ni79Fe21 (5 nm)/Ir22Mn78 (12 nm)/Co62Fe20B18 (4 nm)/MgO(d)/Al(0.8 nm)-oxide/Co62Fe20B18 (6 nm)/Cu(30 nm)/Ta(5 nm) on a thermally oxidized Si wafer substrate were fabricated by magnetron sputtering and photolithographic patterning method. The tunnel magnetoresistance (TMR) and the bias dependence of TMR at room temperature for the MTJs with different thickness d of MgO are investigated. TMR values of over 50% as high as those of the MTJs with pure Al-O barrier and the TMR-voltage curve asymmetries, which vary with the increase of d, are observed in the MTJs with hybrid barriers after annealing at 265℃ for an hour. The dependences of TMR, resistance and coercivity of the MTJs with composite barriers on temperature are also investigated.     

让学生的知识来一个新的认识——浅谈如何上好高三化学总复习课

如何上好高三化学总复习课,历来是化学教学中的一个难题。常见的往往有两种做法（一）“炒冷饭式”复习,就是把过去学过的知识提出来,再重新讲一遍做些题目（二）“梳辫子式”复习,把过去学过的知识系统整理一下,使学生掌握一定的条理。两种做法,前者把知识仅仅作机械的反复,学生易厌倦,不利于调动学生积极性;后者把知识系统整理,虽有利学生对知识的记忆,但仍未达到总复习课的目的。     

在初中几何教学中我是怎样培养与提高学生的解题能力的

教学,就是使学生在教师有计划的、有系统的指导之下,获得一定程度的知识、技能和熟练技巧的过程.知识是对各种事物的特殊性和普遍性及对它们的体系的了解.就其表现形式来看,它们往往以规律、定理及原则等出现.而事物的普遍性,一般寓于特殊之中;一切原则,又往往是隐藏于本质之中.但是一旦把某些个别的、具体的事物所具有的共同的本质属性集中起来,就具有较之个别的、具体的事物更普遍的意义.因此,在教学过程中,教师不仅应把科学