Highly strain-sensitive magnetostrictive tunnel magnetoresistance junctions
Highly strain-sensitive magnetostrictive tunnel magnetoresistance junctions
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DOI：
10.1016/j.jmmm.2015.01.083
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发表时间：
2015-06-15
影响因子：
2.7
通讯作者：
Meyners, Dirk
中科院分区：
文献类型：
--
作者：
Tavassolizadeh, Ali;Hayes, Patrick;Meyners, Dirk
具有CoFeB/MgO/CoFeB层的隧道磁阻（TMR）结因其高TMR效应和磁致伸缩敏感层（CoFeB），在应变传感应用中具有良好前景。即使是亚微米尺寸的TMR结也可用作微机电系统器件的应变传感器。施加应力时，由于逆磁致伸缩效应，这种结的磁化配置会发生变化，从而导致应变敏感的隧道电阻。在此，使用四点弯曲装置在宏观悬臂上研究了直径为11.3μm、19.2μm、30.5μm和41.8μm的圆形结的应变灵敏度。这项研究主要关注由应力诱导的各向异性引起的硬轴TMR回线的变化。提出了一个宏观自旋模型，并通过微磁模拟进行了验证，该模型描述了在高应力下结的TMR回线内敏感层磁化的完全旋转。在拉伸应变低于0.2%时，一个直径为30.5μm的代表性结呈现出2150的非常大的应变系数。对于如此高的应变系数，在与参考层的固定磁化方向成3π/2的角度施加偏置场H = 3.2 kA/m。应变灵敏度强烈依赖于偏置场。沿着与诱导的磁晶各向异性成π/4的方向施加应力，通过一个独特的传感器可以识别压缩应变和拉伸应变。更重要的是，开发了一种在零偏置场下应变系数为400的配置，这导致了一种简单而紧凑的测量装置。（C）2015 Elsevier B.V.保留所有权利。
Tunnel magnetoresistance (TMR) junctions with CoFeB/MgO/CoFeB layers are promising for strain sensing applications due to their high TMR effect and magnetostrictive sense layer (CoFeB). TMR junctions available even in submicron dimensions can serve as strain sensors for microelectromechanical systems devices. Upon stress application, the magnetization configuration of such junctions changes due to the inverse magnetostriction effect resulting in strain-sensitive tunnel resistance. Here, strain sensitivity of round-shaped junctions with diameters of 11.3 mu m, 19.2 mu m, 30.5 mu m, and 41.8 mu m were investigated on macroscopic cantilevers using a four-point bending apparatus. This investigation mainly focuses on changes in hard-axis TMR loops caused by the stress-induced anisotropy. A macrospin model is proposed, supported by micromagnetic simulations, which describes the complete rotation of the sense layer magnetization within TMR loops of junctions, exposed to high stress. Below 0.2%,. tensile strain, a representative junction with 30.5 pm diameter exhibits a very large gauge factor of 2150. For such high gauge factor a bias field H = 3.2 kA/m is applied in an angle equal to 3 pi 2 toward the pinned magnetization of the reference layer. The strain sensitivity strongly depends on the bias field. Applying stress along pi/4 against the induced magnetocrystalline anisotropy, both compressive and tensile strain can be identified by a unique sensor. More importantly, a configuration with a gauge factor of 400 at zero bias field is developed which results in a straightforward and compact measuring setup. (C) 2015 Elsevier B.V. All rights reserved,