NiO和(Pt/Co)多层膜的交换耦合作用及对其矫顽力的影响  

Exchange Coupling between NiO and(Pt/Co) Multilayer and Control of Multilayer's Coercivity

作　　者：刘帅[1] 俱海浪[1,2] 刘洋[1] 李宝河[2] 于广华[1] 

机构地区：[1]北京科技大学材料科学与工程学院,北京100083 [2]北京工商大学理学院,北京100048

出　　处：《稀有金属》2015年第1期23-28,共6页Chinese Journal of Rare Metals

基　　金：国家自然科学基金项目(51371027;11174020)资助

摘　　要：研究了用磁控溅射法制备的(Pt/Co)多层膜和绝缘体反铁磁材料NiO之间的磁学和晶体学相互作用。室温下,当NiO覆盖在(Pt/Co)多层膜上面且NiO厚度大于25 nm时观察到了交换偏置,偏置场随NiO厚度的增加而增大。但总体上偏置场(HE)很小,对应NiO厚度为120nm时偏置场不到4000 A·m-1。NiO在(Pt/Co)多层膜下面时没有观察到交换偏置,但是对多层膜的矫顽力和垂直磁各向异性产生了很大影响。(Pt/Co)多层膜的矫顽力随NiO厚度的增加呈现非单调衰减趋势,当NiO厚度为1和3 nm时,矫顽力分别出现极小值和极大值,厚度超过3 nm的NiO使矫顽力单调下降,直至减小到接近零。(Pt/Co)多层膜的垂直磁各向异性随底层NiO厚度的增加逐渐变弱,最后垂直方向变为难轴。矫顽力和垂直磁各向异性的这种变化是由超薄NiO和(Pt/Co)多层膜之间可能存在的邻近效应,弱晶化NiO对(Pt/Co)多层膜(111)织构的影响以及NiO与(Pt/Co)多层膜之间的交换耦合共同作用造成的。The magnetic and crystallographic interaction between（Pt/Co） multilayer and insulating antiferromagnetic NiO layer prepared by magnetron sputtering was explored. Room-temperature exchange bias was observed in（Pt/Co）-NiO system when NiO layer was thicker than 25 nm and deposited on top of（Pt/Co） multilayer. The exchange bias field（HE）,which increased with the NiO layer thickness increasing,was generally very small（about 4000 A·m^-1 corresponding to 120 nm thick NiO layer）. When the NiO layer was deposited below the（Pt/Co） multilayer,no exchange bias was detected,but the coercivity（HC） and perpendicular magnetic anisotropy of the（Pt/Co） multilayer were greatly affected. With the thickness of the NiO layer increasing,the coercivity exhibited a nonmonotonic decay. 1 and 3 nm thick NiO layers corresponded to the minimum and maximum values of the coercivity,respectively. Thicker NiO layer exceeding 3 nm reduced the coercivity to near zero. The perpendicular magnetic anisotropy of the（Pt/Co） multilayer got weakened by NiO underlayer and finally the vertical direction became hard axis. This phenomenon was ascribed to the possible proximity effect between thin NiO layer and ferromagnetic（Pt/Co） multilayer,the effect of weak crystallized NiO layer on the（111） texture of（Pt/Co） multilayer and the exchange coupling between NiO layer and（Pt/Co） multilayer.

关 键 词：交换耦合 交换偏置 (Pt/Co)多层膜 NIO 

分 类 号：O484.43[理学—固体物理]