Measurements, Technology, and Layout of Sensitive Anisotropic Magnetoresistive Sensors (original) (raw)
Related papers
The European Physical Journal Applied Physics, 2006
We report on the characterization of the behaviour of an anisotropic magnetoresistive sensor undergoing a 100 kHz flipping of the magnetic domains, i.e. at frequencies two/three orders of magnitude higher than conventionally recommended. The noise analysis allows for the optimal setting of the relevant parameters defining such high-frequency, and hitherto unexplored, operation regime. Precision and accuracy performance in static conditions have been assessed by keeping into account the role of the sensor temperature. This last parameter has been evaluated by suitably manipulating the signals occurring at the sensor itself. The used technique can provide the base for a temperature sensor conditioning to be employed in magnetometers using this kind of devices.
LOW FIELD MAGNETIC SENSING WITH ANISOTROPIC MAGNETORESISTIVE SENSORS
Large quantities of magnetic field investigations are routinely gathered over space exploration. Results of those measurements can provide important information about Earth, planets and other cosmic objects because their bodies and surfaces containing proportions of materialswith a different magnetic susceptibility. Besides conventional requirements satellite magnetic measurement equipment need to be robust for high mechanical vibrations, radiation persistency and operate at a very wide temperature range. Various magnetic sensors are available for space use. In the report, we discuss suitability of AMR application in satellites.
Recent Developments of Magnetoresistive Sensors for Industrial Applications
Sensors, 2015
The research and development in the field of magnetoresistive sensors has played an important role in the last few decades. Here, the authors give an introduction to the fundamentals of the anisotropic magnetoresistive (AMR) and the giant magnetoresistive (GMR) effect as well as an overview of various types of sensors in industrial applications. In addition, the authors present their recent work in this field, ranging from sensor systems fabricated on traditional substrate materials like silicon (Si), over new fabrication techniques for magnetoresistive sensors on flexible substrates for special applications, e.g., a flexible write head for component integrated data storage, micro-stamping of sensors on arbitrary surfaces or three dimensional sensing under extreme conditions (restricted mounting space in motor air gap, high temperatures during geothermal drilling).
On Wafer Characterisation of the Analog Anisotropic Magnetoresistance Sensor
2020
This article presents the solution for a fast evaluation tool of an analog integrated Anisotropic Magnetoresistance Sensor (AMR) on a silicon wafer. It was necessary to evaluate a selected prototype development phase of a custom analog AMR sensor. This approach significantly shortened the development time as no dicing and packaging was required. We will also use this solution later for a final volume production wafer sorting. The biggest challenge was to quickly generate and release an accurate, sufficiently strong magnetic field that is as parallel as possible to the wafer surface. Such a field is needed to measure the peak values of the sine and cosine output signals of the analog AMR sensor.
Permanent-magnet-free stabilization and sensitivity tailoring of magnetoresistive field sensors
Journal of Applied Physics, 2007
We have exploited the coupling across a ruthenium spacer between a ferromagnetic and an antiferromagnetic layer to stabilize the magnetization in a given direction and tailor the magnetic sensitivity of the sensor for various applications. Ruthenium is used as the nonmagnetic coupling layer and is self-aligned with the ferromagnetic free layer and antiferromagnetic pinning layer, and the thickness is varied to change the slope of the transfer curve in the linear region, i.e., sensitivity. This simple technique is shown to increase the dynamic range of anisotropic magnetoresistive sensors without additional lithography.
Magnetoresistance sensors with magnetic layers for high sensitivity measurements
In this study we present an overview of the sensors made from magnetic layers and nanostructured systems. Fundamental and technological aspects are presented. A review of the spin valve mechanism is presented. A spin valve device consists of two ferromagnetic layers, separated by a Cu spacer. When the Cu layer is replaced by a thin insulator layer (Al2O3) then, we have a magnetic tunnel junction or, for some deposition conditions, a nanogranular system. Electrical and magnetic characterization of the magnetic layers and nanogranular systems plays an important role in the designing process of these sensors and some results are presented in this paper. For a better understanding of the magnetization processes that take place in these systems, micromagnetic simulations were performed as well. Finally, we present a method to increase the response quality of a rotation sensor based on the anisotropic magnetoresistance effect and a detection system of the magnetic particles employed in biology as markers or as carriers for targeted drug delivery.
Journal of Physics-condensed Matter, 2007
Magnetoresistive sensors using spin valves and magnetic tunnel junctions are reviewed, considering applications as readers in hard disk drives, as well as applications where the ultimate field detection limits are required (from nT down to pT). The sensor noise level in quasi-DC or high-frequency applications is described, leading to sensor design considerations concerning biomedical and read head applications. Magnetic tunnel junction based sensors using MgO barriers appear as the best candidates for ultra-low field (pT) detection, either in the high-frequency regime, or for quasi-DC applications.
Flipping field and stability in anisotropic magnetoresistive sensors
Sensors and Actuators A: Physical, 2003
Switched-capacitor flipping circuits developed for Philips KMZ51 and KMZ52 anisotropic magnetoresistance (AMR) sensors give up to 2.8 A/1 kHz current peaks. Such unusually high current deeply saturates the sensor and thus removes hysteresis, reduces noise, and increases the resistance against field shocks. These necessary strong flipping fields are predicted by the energetic model (EM), applied to the magnetization reversal in thin films. The EM parameters have been correlated to microscopic variables, revealing the field dependence of the speed of magnetization reversal. This is responsible for the value of the critical switching field (and therefore for the stability of the AMR sensor) in the easy axis directions, depending on the saturating field amplitude.
Noise in small magnetic systems—applications to very sensitive magnetoresistive sensors
Journal of Magnetism and Magnetic Materials, 2005
Reduction for 1/f noise (or random telegraph noise) is a crucial issue for small magnetic sensors which is strongly related to structural properties and magnetic configuration. We show how it is possible to eliminate magnetic noise at low frequency in GMR/TMR sensors by a combination of cross anisotropies, window frame shapes and suitably designed magnetoresisitive stack. These sensors are superior to almost all existing field and flux sensors. Results are presented on a mixed sensor, where a superconducting loop acts as a flux-to-field transformer to the GMR sensor. This device is suitable for detection of biomagnetic signals, such as in magnetocardiography or in magnetoencephalography. Measurements on niobium-based and YBCO-based sensors are presented, leading to sensitivity of 30fT/ Hz at 77K for small samples. Sensitivity lower than 1fT/ (Hz) is expected with appropriate design and use of TMR or CMR layers, which makes these a powerful alternative to SQUIDs.