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Order of magnitude increase in AMR sensor layer thickness through multi-interface exchange biasing
KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH. (Applied spintronics)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We demonstrate an order of magnitude increase in total ferromagnetic layer thickness in magnetron sputtered and exchange-biased multilayers of [IrMn(15nm)/NiFe(t)]N/IrMn(15nm) with t=50{200 nm and N=1{7. Wend a strong exchange-bias eld (Heb) and a low coercivity (Hc) in all multilayers, with a gradual improvement with increasing number of multilayer repetitions. All stacks with t=50{150 nm exhibit single-step switching,while the stacks with the thickest NiFe show signs of multistep switching. Four-point magnetotransport measurements show values for the anisotropic magnetoresistance (AMR) of about 3% in all stacks. We determine the lm roughness and mean grain size using Atomic Force Microscopy and nd a direct correlation between Heb and the grain size on the one hand, and Hc and the inverse of the roughness on the other. Our results directly demonstrate the feasibility

Keyword [en]
AMR, Magnetic sensor, Ferromagnetic, Antiferromagnetic, NiFe, IrMn, exchange bias
National Category
Condensed Matter Physics
Research subject
Physics; Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-187232OAI: oai:DiVA.org:kth-187232DiVA: diva2:929317
Note

QC 20160519

Available from: 2016-05-18 Created: 2016-05-18 Last updated: 2016-05-19Bibliographically approved
In thesis
1. Fabrication and Characterization of magnetometer for space applications
Open this publication in new window or tab >>Fabrication and Characterization of magnetometer for space applications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 73 p.
Series
TRITA-ICT, 2016:15
Keyword
AMR, Magnetic sensor, Ferromagnetic, Antiferromagnetic, NiFe, IrMn, exchange bias.
National Category
Condensed Matter Physics
Research subject
Physics; Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-187237 (URN)ISBN 978-91-7595-982-5 (ISBN)
Public defence
2016-06-10, Sal C, Isafjordsgatan 26, Kista, 13:01 (English)
Opponent
Supervisors
Available from: 2016-05-19 Created: 2016-05-18 Last updated: 2016-05-19Bibliographically approved

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