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Title: Combined magnetic X-ray and polarized neutron reflectivity studyof the origins of exchange bias in the Co/FeF2 system

Abstract

We discuss studies of the magnetic specular reflectivity ofneutrons and X-rays from the exchange bias system consisting of a singlecrystal film of antiferromagnetic FeF2 capped with a ferromagnetic Cofilm cooled in an applied magnetic field below the TN of the FeF2. Thissystem exhibits a shift of the magnetic hysteresis loop along thedirection of the cooling field Hc (positive exchange bias) or in theopposite direction (negative exchange bias) depending on the magnitude ofthe cooling field. The use of neutrons with polarization analysis enablesthe spatial distribution of different vector components of themagnetization to be determined, and the use of resonant magnetic X-rayscattering enables magnetization in a compound system to be determinedelement-selectively. Our results show that the coupling across theinterface between the relatively few uncompensated Fe spins and the morenumerous Co spins is antiferromagnetic. In a large cooling field whichoverrides this coupling, the Fe spins are oriented along Hc and some getpinned in this direction, in turn pinning the Co spins above theinterface oppositely and thus creating positive exchange bias. For sallvalues of Hc the Fe spins get locked in the opposite direction producingnegative exchange bias. In addition a significant fraction of the Fespins at the interface are unpinned and always align oppositemore » to the Comagnetization.« less

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
COLLABORATION - UCSD
OSTI Identifier:
932975
Report Number(s):
LBNL-63340
Journal ID: SUMIEK; R&D Project: 504103; TRN: US200814%%185
DOE Contract Number:  
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Superlattices and Microstructures; Journal Volume: 41; Journal Issue: 2-3; Related Information: Journal Publication Date: online05/07/2007
Country of Publication:
United States
Language:
English
Subject:
75; 36; HYSTERESIS; MAGNETIC FIELDS; MAGNETIZATION; MONOCRYSTALS; NEUTRONS; POLARIZATION; REFLECTIVITY; SCATTERING; SPATIAL DISTRIBUTION; VECTORS; exchange bias, uncompensated spins, antiferromagnetism, x-rayreflectivity, neutron reflectivity

Citation Formats

Fitzsimmons, M.R., Roy, S., Kirby, B.J., Park, S., Roshchin, IgorV., Li, Zhi-Pan, Kortright, J.B., Sinha, S.K., and Schuller, Ivan K. Combined magnetic X-ray and polarized neutron reflectivity studyof the origins of exchange bias in the Co/FeF2 system. United States: N. p., 2007. Web. doi:10.1016/j.spmi.2007.02.004.
Fitzsimmons, M.R., Roy, S., Kirby, B.J., Park, S., Roshchin, IgorV., Li, Zhi-Pan, Kortright, J.B., Sinha, S.K., & Schuller, Ivan K. Combined magnetic X-ray and polarized neutron reflectivity studyof the origins of exchange bias in the Co/FeF2 system. United States. doi:10.1016/j.spmi.2007.02.004.
Fitzsimmons, M.R., Roy, S., Kirby, B.J., Park, S., Roshchin, IgorV., Li, Zhi-Pan, Kortright, J.B., Sinha, S.K., and Schuller, Ivan K. Wed . "Combined magnetic X-ray and polarized neutron reflectivity studyof the origins of exchange bias in the Co/FeF2 system". United States. doi:10.1016/j.spmi.2007.02.004.
@article{osti_932975,
title = {Combined magnetic X-ray and polarized neutron reflectivity studyof the origins of exchange bias in the Co/FeF2 system},
author = {Fitzsimmons, M.R. and Roy, S. and Kirby, B.J. and Park, S. and Roshchin, IgorV. and Li, Zhi-Pan and Kortright, J.B. and Sinha, S.K. and Schuller, Ivan K.},
abstractNote = {We discuss studies of the magnetic specular reflectivity ofneutrons and X-rays from the exchange bias system consisting of a singlecrystal film of antiferromagnetic FeF2 capped with a ferromagnetic Cofilm cooled in an applied magnetic field below the TN of the FeF2. Thissystem exhibits a shift of the magnetic hysteresis loop along thedirection of the cooling field Hc (positive exchange bias) or in theopposite direction (negative exchange bias) depending on the magnitude ofthe cooling field. The use of neutrons with polarization analysis enablesthe spatial distribution of different vector components of themagnetization to be determined, and the use of resonant magnetic X-rayscattering enables magnetization in a compound system to be determinedelement-selectively. Our results show that the coupling across theinterface between the relatively few uncompensated Fe spins and the morenumerous Co spins is antiferromagnetic. In a large cooling field whichoverrides this coupling, the Fe spins are oriented along Hc and some getpinned in this direction, in turn pinning the Co spins above theinterface oppositely and thus creating positive exchange bias. For sallvalues of Hc the Fe spins get locked in the opposite direction producingnegative exchange bias. In addition a significant fraction of the Fespins at the interface are unpinned and always align opposite to the Comagnetization.},
doi = {10.1016/j.spmi.2007.02.004},
journal = {Superlattices and Microstructures},
number = 2-3,
volume = 41,
place = {United States},
year = {Wed Feb 07 00:00:00 EST 2007},
month = {Wed Feb 07 00:00:00 EST 2007}
}