Optimised GMR sensors for low and high frequencies applications
Optimised GMR sensors for low and high frequencies applications
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DOI：
10.1016/j.sna.2005.11.043
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发表时间：
2006-05-24
影响因子：
4.6
通讯作者：
Cousin, B.
中科院分区：
文献类型：
--
作者：
Fermon, C.;Pannetier-Lecoeur, M.;Cousin, B.
磁阻传感器，特别是GMR和TMR传感器非常敏感，但是它们用于非常精确的测量的用途通常受到它们在所施加磁场中的行为的限制。第一个约束是建立无磁滞自旋阀，这对于提供对大的随机磁场的有效免疫力和确保测量的再现性是必要的。第二个约束是传感器在工作区域中的线性。最后，降低噪声，特别是磁噪声对于GMR和TMR用作传感器是必不可少的。磁滞仅取决于自旋阀的组成和形状。耦合到交叉各向异性的软层的厚度起着重要的作用。极化中子反射仪显示了软层中存在的小旋转，这一点得到了强调。形状各向异性也有很大的影响滞后，但有灵敏度和滞后自由systems.GMR和TMR传感器是非线性的，这个缺点限制了它们作为霍尔传感器的替代品，在大量的应用灵敏度是不重要的竞争。我们将展示如何通过结合设计和反馈电子来克服这个问题。噪声特性对于非常敏感的传感器也是至关重要的。在低频，1/f噪声占主导地位的热噪声，它是有关的结构缺陷和磁配置。通过传感器的适当设计，可以抑制1/f磁噪声。对自旋阀的非线性采用双调制技术也可以降低1/f结构噪声。(c)2005 Elsevier B. V.保留所有权利。
Magnetoresistive sensors and in particular GMR and TMR sensors are very sensitive but their use for very accurate measurements is often limited by their behaviour in applied magnetic fields.A first constraint is the building of hysteresis free spin valves which is necessary to give an efficient immunity against large random magnetic fields and insure reproducibility of the measurements. A second constraint is the linearity of the sensor in the working region. Finally, the reduction of noise and in particular the magnetic noise is essential for the use of GMR and TMR as sensors.The hysteresis is only dependent on the composition and the shape of the spin valve. The thickness of the soft layer coupled to cross anisotropies plays an important role. This has been highlighted by polarised neutron reflectometry which has shown the existence of small rotations in the soft layer. The shape anisotropy has also a strong influence on the hysteresis but there is a competition between sensitivity and hysteresis free systems.GMR and TMR sensors are nonlinear and this drawback limits their use as replacement of Hall sensors for a large number of applications where sensitivity is not crucial. We will show how we can overcome this problem by combining the design and feedback electronics.Noise behaviour is also crucial for very sensitive sensors. At low frequencies, 1/f noise dominates the thermal noise; it is related to structural defects and magnetic configuration. By a proper design of the sensor, 1/f magnetic noise can be suppressed. A 1/f structural noise can also be reduced by using double modulation technique on the nonlinearity of the spin valve. (c) 2005 Elsevier B.V. All rights reserved.