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Title: Exchange coupling between ferromagnetic and antiferromagnetic layers via Ru and application for a linear magnetic field sensor

Abstract

Exchange coupling is observed in a trilayer structure of ferromagnet-Ru-antiferromagnet and the coupling strength is found to be a function of the thickness of the Ru spacer layer. This is the first observation for such a trilayer structure and may help to shed light on the illusive mechanism of exchange coupling in these systems. This unique coupling is used to bias the sense layer in a magnetic tunnel junction structure so that the magnetization orientations of the sense layer and the pinned layer can be independently controlled. Sensor devices are fabricated with a bipolar output, a medium sensitivity, and a wide field range. The results show that this biasing scheme is well suited for magnetic tunnel junctions used in magnetic field sensors.

Authors:
; ; ; ;  [1]
  1. NVE Corporation, 11409 Valley View Road, Eden Prairie, Minnesota 55344 (United States)
Publication Date:
OSTI Identifier:
20788135
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 99; Journal Issue: 8; Other Information: DOI: 10.1063/1.2162507; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANTIFERROMAGNETIC MATERIALS; ANTIFERROMAGNETISM; EXCHANGE INTERACTIONS; FERROMAGNETIC MATERIALS; LAYERS; MAGNETIC FIELDS; MAGNETIZATION; RUTHENIUM; SUPERCONDUCTING JUNCTIONS; THICKNESS; TUNNEL EFFECT

Citation Formats

Wang Dexin, Daughton, Jim, Nordman, Cathy, Eames, Pete, and Fink, Jon. Exchange coupling between ferromagnetic and antiferromagnetic layers via Ru and application for a linear magnetic field sensor. United States: N. p., 2006. Web. doi:10.1063/1.2162507.
Wang Dexin, Daughton, Jim, Nordman, Cathy, Eames, Pete, & Fink, Jon. Exchange coupling between ferromagnetic and antiferromagnetic layers via Ru and application for a linear magnetic field sensor. United States. doi:10.1063/1.2162507.
Wang Dexin, Daughton, Jim, Nordman, Cathy, Eames, Pete, and Fink, Jon. Sat . "Exchange coupling between ferromagnetic and antiferromagnetic layers via Ru and application for a linear magnetic field sensor". United States. doi:10.1063/1.2162507.
@article{osti_20788135,
title = {Exchange coupling between ferromagnetic and antiferromagnetic layers via Ru and application for a linear magnetic field sensor},
author = {Wang Dexin and Daughton, Jim and Nordman, Cathy and Eames, Pete and Fink, Jon},
abstractNote = {Exchange coupling is observed in a trilayer structure of ferromagnet-Ru-antiferromagnet and the coupling strength is found to be a function of the thickness of the Ru spacer layer. This is the first observation for such a trilayer structure and may help to shed light on the illusive mechanism of exchange coupling in these systems. This unique coupling is used to bias the sense layer in a magnetic tunnel junction structure so that the magnetization orientations of the sense layer and the pinned layer can be independently controlled. Sensor devices are fabricated with a bipolar output, a medium sensitivity, and a wide field range. The results show that this biasing scheme is well suited for magnetic tunnel junctions used in magnetic field sensors.},
doi = {10.1063/1.2162507},
journal = {Journal of Applied Physics},
number = 8,
volume = 99,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}
  • The effect of the growth conditions and the Mn concentration on the exchange coupling between a ferromagnetic (F) NiFe and an antiferromagnetic (AF) MnNi layers were studied. We found that an F/AF coupling appears in the bilayers when the Mn concentration is more than 45%. Beyond this critical concentration the exchange field shows a maximum then decreases. The correlation between the exchange field and the microstructure of the film is discussed. We show that: (1) the enhancement of the exchange field is associated with the enhancement of the antiferromagnetic grain size and (2) the existence of the exchange field ismore » associated with a third x-ray peak which may be an FeMnNi ternary allow type. This result was associated with interfacial diffusion confirmed by magnetization variation measurements before and after annealing. {copyright} 2001 American Institute of Physics.« less
  • The magnetic behavior of Fe lines on top of a continuous FeF{sub 2} antiferromagnetic layer was investigated as a function of the orientation of the lines with respect to the applied magnetic field and a unidirectional anisotropy established by field cooling. The orientational dependence of the asymmetric loop shift, called exchange bias, shows that the competition between shape and unidirectional anisotropies modifies the exchange bias and the coercivity. Remarkably, in certain cases, exchange bias can be observed even when the applied field is perpendicular to the unidirectional anisotropy. Numerical simulations with a coherent rotation model illustrate a rich phase diagram,more » which originates from the noncollinearity of the involved anisotropies. Using this phase diagram, exchange bias and coercivity can be predictably tailored. In particular, different preferred magnetization directions can be designed in separately patterned structures of the same sample with identical preparation and magnetic history.« less
  • Highlights: • Effect of Mn-site doping by Ru has been studied in La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7}. • Electrical resistance, magnetoresistance and magnetic properties were measured. • Ru substitution enhances the ferromagnetism and metallicity. • Results were interpreted by the ferromagnetically coupled Ru with Mn ions in Mn–O–Ru network. - Abstract: The effect of Mn-site doping on magnetic and transport properties in the bilayer manganites La{sub 1.24}Sr{sub 1.76}Mn{sub 2-y}Ru{sub y}O{sub 7} (y = 0.0, 0.04, 0.08 and 0.15) has been studied. The undoped compound La{sub 1.24}Sr{sub 1.76}Mn{sub 2}O{sub 7} exhibits a ferromagnetic metal to paramagnetic insulator transition at T{submore » C} = 130 K and the substitution of Ru shifts the transition temperatures to higher temperature values. The increased metal–insulator transition by Ru substitution, obtained from temperature dependence of resistivity measurements, indicates that the Ru substitution enhances the metallic state at low temperature regime and favours the Mn–Ru pairs in the Ru doped samples. Moreover, the activation energy values calculated from the temperature dependence of resistivity curves suggest that the Ru substitution weakens the formation of polarons. The increased magnetoresistance ratio from 108% to 136% by Ru substitution, measured at 5 K, points out that the Ru substitution also enhances the inter-grain tunneling magnetoresistance. Thus, the ferromagnetic order and metallic state in La{sub 1.24}Sr{sub 1.76}Mn{sub 2}O{sub 7} system have been enhanced by the presence of Ru in the Mn-site. These reinforcements of ferromagnetic metallic state and magnetoresistance have been interpreted by the ferromagnetically coupled high spin states of Ru with Mn ions in the Mn–O–Ru network.« less