Fabrication and Characterization of magnetometer for space applications

• Main Author: Qejvanaj, Fatjon
• Format: Doctoral Thesis
• Language: English
• Published: KTH, Materialfysik, MF 2016
• Subjects: AMR; Magnetic sensor; Ferromagnetic; Antiferromagnetic; NiFe; IrMn; exchange bias.
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-187237; http://nbn-resolving.de/urn:isbn:ISBN 978-91-7595-982-5

The present rapid increase in the number of space missions demands a decrease in the cost of satellite equipment, but also requires the development of instruments that have low power consumption, low weight, and small size.Anisotropic magnetoresistance (AMR) sensors can answer these needs on account of their small size, weight, and power consumption. AMR sensors also produce lower noise than either giant magnetoresistance (GMR) or tunnel magnetoresistance (TMR) devices and are thus more suitable for space applications.The type of AMR sensor developed in this study was a Planar Hall EffectBridge (PHEB) sensor. The FM layer was also coupled with an AFM layer in order to fix the internal magnetization of the FM layer.One technique that was employed in order to meet the low-noise requirement was to make the FM layer thicker than has previously been attempted.In doing so, the exchange bias field between the AFM layer and the FMlayer is no longer high enough to bias the thicker FM layer, so in order to correct this unwanted effect, the material stack was upgraded to two AFM–FM interfaces. With this configuration, it became possible to increase the exchange field by up to 60%. Stronger exchange bias leads to a thicker FMlayer and so to lower noise in the device performance. Another strategy that was used to lower the resistance of the device was to implement an NiFeX alloy instead of the standard NiFe. NiFeX consists of an alloy of NiFe andCu, Ag, or Au; the last of these is known to have very low resistivity.This solution leads to a significant lowering of the device’s resistance. A recent technological advance used to fabricate devices with lower resistance is to deposit a multilayer of AFM–FM.