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Title: Domain structure and magnetization reversal ofantiferromagnetically coupled perpendicular anisotropy films

Abstract

We describe experimental and theoretical investigations ofthe magnetic domain formation and the field reversal behavior inantiferromagnetically coupled perpendicular anisotropy multilayers thatmimic A-type antiferromagnet (AF) structures. The samples are sputterdeposited Co/Pt multilayers with perpendicular anisotropy that areperiodically interleaved with Ru to mediate an antiferromagneticinterlayer exchange. This structure allows precise tuning of thedifferent magnetic energy terms involved. Using various magnetometry andmagnetic imaging techniques as well as resonant soft X-ray scattering weprovide a comprehensive study of the remanent and demagnetizedconfigurations as well as the corresponding reversal mechanisms. We findthat adding AF exchange to perpendicular anisotropy system alters thetypical energy balance that controls magnetic stripe domain formation,thus resulting in two competing reversal modes for the composite system.In the AF-exchange dominated regime the magnetization isferromagnetically ordered within the film plane with the magnetization ofadjacent layers anti-parallel thus minimizing the interlayer AF exchangeenergy. In the dipolar dominated regime the magnetization pattern formsferromagnetic (FM) stripe domains where adjacent layers are verticallycorrelated, but laterally anti-correlated thus minimizing the dipolarenergy at the expense of the AF interlayer coupling. By tuning the layerthickness or applying a magnetic field, we observed the co-existence ofAF domains and FM stripe domains. We find that a FM phase exists at AFdomain boundaries, causing complexmore » mesoscopic domain patterns withsurprising reversibility during minor loop field cycling.« less

Authors:
; ; ;
Publication Date:
Research Org.:
COLLABORATION - Hitachi Global StorageTechnologies
OSTI Identifier:
929667
Report Number(s):
LBNL-63341
Journal ID: ISSN 0304-8853; JMMMDC; R&D Project: 504103; TRN: US200812%%740
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Magnetism and Magnetic Materials; Journal Volume: 319; Journal Issue: 1-2; Related Information: Journal Publication Date: online05/08/2007
Country of Publication:
United States
Language:
English
Subject:
75; 36; ANISOTROPY; DOMAIN STRUCTURE; ENERGY BALANCE; MAGNETIC FIELDS; MAGNETIZATION; SCATTERING; THICKNESS; TUNING; Layered antiferromagnet; Perpendicular anisotropy; Domainstructure; Reversal mechanism; AF exchange coupling; Stripedomain

Citation Formats

Hellwig, Olav, Berger, Andreas, Kortright, Jeffrey B., and Fullerton,Eric E.. Domain structure and magnetization reversal ofantiferromagnetically coupled perpendicular anisotropy films. United States: N. p., 2007. Web. doi:10.1016/j.jmmm.2007.04.035.
Hellwig, Olav, Berger, Andreas, Kortright, Jeffrey B., & Fullerton,Eric E.. Domain structure and magnetization reversal ofantiferromagnetically coupled perpendicular anisotropy films. United States. doi:10.1016/j.jmmm.2007.04.035.
Hellwig, Olav, Berger, Andreas, Kortright, Jeffrey B., and Fullerton,Eric E.. Fri . "Domain structure and magnetization reversal ofantiferromagnetically coupled perpendicular anisotropy films". United States. doi:10.1016/j.jmmm.2007.04.035.
@article{osti_929667,
title = {Domain structure and magnetization reversal ofantiferromagnetically coupled perpendicular anisotropy films},
author = {Hellwig, Olav and Berger, Andreas and Kortright, Jeffrey B. and Fullerton,Eric E.},
abstractNote = {We describe experimental and theoretical investigations ofthe magnetic domain formation and the field reversal behavior inantiferromagnetically coupled perpendicular anisotropy multilayers thatmimic A-type antiferromagnet (AF) structures. The samples are sputterdeposited Co/Pt multilayers with perpendicular anisotropy that areperiodically interleaved with Ru to mediate an antiferromagneticinterlayer exchange. This structure allows precise tuning of thedifferent magnetic energy terms involved. Using various magnetometry andmagnetic imaging techniques as well as resonant soft X-ray scattering weprovide a comprehensive study of the remanent and demagnetizedconfigurations as well as the corresponding reversal mechanisms. We findthat adding AF exchange to perpendicular anisotropy system alters thetypical energy balance that controls magnetic stripe domain formation,thus resulting in two competing reversal modes for the composite system.In the AF-exchange dominated regime the magnetization isferromagnetically ordered within the film plane with the magnetization ofadjacent layers anti-parallel thus minimizing the interlayer AF exchangeenergy. In the dipolar dominated regime the magnetization pattern formsferromagnetic (FM) stripe domains where adjacent layers are verticallycorrelated, but laterally anti-correlated thus minimizing the dipolarenergy at the expense of the AF interlayer coupling. By tuning the layerthickness or applying a magnetic field, we observed the co-existence ofAF domains and FM stripe domains. We find that a FM phase exists at AFdomain boundaries, causing complex mesoscopic domain patterns withsurprising reversibility during minor loop field cycling.},
doi = {10.1016/j.jmmm.2007.04.035},
journal = {Journal of Magnetism and Magnetic Materials},
number = 1-2,
volume = 319,
place = {United States},
year = {Fri Mar 16 00:00:00 EDT 2007},
month = {Fri Mar 16 00:00:00 EDT 2007}
}
  • The microstructure and magnetic properties of Nd-Fe-B films with thicknesses from 100 nm to 3 nm have been investigated. All the films show excellent perpendicular magnetic anisotropy with a squareness ratio of 1 in the perpendicular direction and almost zero coercivity in the in-plane direction. Of particular interest is that the initial magnetization curves sensitively depended on the film thickness. Films thicker than 15 nm show steep initial magnetization curve. Although the films have coercivities larger than 21 kOe, the films can be fully magnetized from the thermally demagnetized state with a field as small as 5 kOe. With themore » decrease of film thickness to 5 nm, the initial magnetization curve becomes flat. The evolution of initial magnetization curves with film thickness can be understood by the microstructure of the films. Films with thickness of 15 nm show close-packed grains without any intergranular phases. Such microstructures lead to steep initial magnetization curves. On the other hand, when the film thickness decreased to 3 nm, the film thickness became nonuniform. Such microstructure leads to flat initial magnetization curves.« less
  • We investigate the reversal process in antiferromagnetically coupled [Co/Pt]{sub X-1}/{l_brace}Co/Ru/[Co/Pt]{sub X-1}{r_brace}{sub 16} multilayer films by combining magnetometry and Magnetic soft X-ray Transmission Microscopy (MXTM). After out-of-plane demagnetization, a stable one dimensional ferromagnetic (FM) stripe domain phase (tiger-tail phase) for a thick stack sample (X=7 is obtained), while metastable sharp antiferromagnetic (AF) domain walls are observed in the remanent state for a thinner stack sample (X=6). When applying an external magnetic field the sharp domain walls of the thinner stack sample transform at a certain threshold field into the FM stripe domain wall phase. We present magnetic energy calculations that revealmore » the underlying energetics driving the overall reversal mechanisms.« less
  • Ultrathin Ni films with perpendicular magnetic anisotropy were deposited on Cu(100) at room temperature. The magnetic properties of the films were measured upon multiple magnetization reversals in an alternating magnetic field using the magneto-optic Kerr effect. All magnetic properties remain virtually constant for up to 10{sup 6} magnetization reversals for all films studied. This finding is supported by a simple theoretical model.
  • Direct observation of the magnetization reversal of epitaxial NiO/NiFe bilayers grown on (001) MgO and on polycrystalline Si substrates was performed by using the magneto-optical indicator film technique. It was shown that the unidirectional-axis magnetization reversal proceeds by domain nucleation and growth. A new phenomenon, an asymmetry in the activity of the domain nucleation centers, has been revealed. Remagnetization of the bilayer is shown to be governed by defect structures in the {ital antiferromagnetic} layer. {copyright} {ital 1998 American Institute of Physics.}