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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Magnetic and Mössbauer study of Fe/Si multilayers

T. Luciński, M. Kopcewicz, A. Hütten, H. Brückl, S. Heitmann, T. Hempel, and G. Reiss

J. Appl. Phys. 93, 6501 (2003); http://dx.doi.org/10.1063/1.1558656 (3 pages) | Cited 6 times

Online Publication Date: 9 May 2003

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The magnetic and structural properties of Fe/Si multilayers (Mls) have been studied by x-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS) methods. Strong antiferromagnetic (AF) coupling J=−1.93 mJ/m2 accompanied by saturation field of 1.5 T has been found for Si layer thickness dSi=1.4 nm. Magnetic moment measurements of Fe/Si Mls vs Fe thickness revealed that 0.25 nm of Fe per single interface is magnetically inactive. The CEMS spectra recorded at room temperature consist of the Zeeman sextet characteristic of the pure Fe phase (hyperfine field of about 32.8 T) accompanied by two spectral components related to FeSi system: magnetic broad sextet and a quadrupole doublet. The broad sextet could originate from various Fe sites at the interface. The nonmagnetic quadrupole split (QS) doublet is most probably associated with the nonstoichiometric c-Fe1−xSix phase. For larger Si layer thickness (dSi>2 nm) the spectral contribution of the QS doublet increases from 5.7% to about 16%. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.65.Ac Multilayers
76.80.+y Mössbauer effect; other γ-ray spectroscopy
75.30.Cr Saturation moments and magnetic susceptibilities
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
71.70.Jp Nuclear states and interactions

Proximity effects at epitaxial Co/FeMn thin film systems (invited)

F. Matthes, A. Rzhevskii, L.-N. Tong, L. Malkinski, Z. Celinski, and C. M. Schneider

J. Appl. Phys. 93, 6504 (2003); http://dx.doi.org/10.1063/1.1555319 (3 pages) | Cited 6 times

Online Publication Date: 9 May 2003

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We prepared exchange-biased Co/FeMn structures to examine the interaction between single crystalline ferromagnetic and antiferromagnetic films with well-defined interfaces. Using x-ray magnetic circular dichroism (XMCD) and magneto-optical Kerr effect we studied in situ layered systems of fcc Co and FeMn epitaxially grown onto Cu(001) templates. XMCD studies reveal that in the FeMn layer a certain fraction of Fe is polarized at the Co/FeMn interface. The magnetic moment on the Fe atoms is parallel to the Co magnetization direction. Compared to Fe the measured dichroic signal for Mn was considerably smaller. Experiments with epitaxially grown trilayer systems of Co/FeMn/Co showed that the proximity of the ferromagnetic material influences the properties of the antiferromagnetic material leading, e.g., to a reduction of the temperature at which a marked increase of the coercive field occurs. Strong ferromagnetic and 90° coupling between the Co films observed at different thicknesses of the FeMn spacer do not affect the proximity effect at the antiferromagnet/ferromagnet interface. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
78.20.Ls Magneto-optical effects
75.50.Ee Antiferromagnetics
75.50.Cc Other ferromagnetic metals and alloys
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.66.Bz Metals and metallic alloys

Hard x-ray magnetic circular dichroism study of a surface-driven twisted state in Gd/Fe multilayers

D. Haskel, Y. Choi, D. R. Lee, J. C. Lang, G. Srajer, J. S. Jiang, and S. D. Bader

J. Appl. Phys. 93, 6507 (2003); http://dx.doi.org/10.1063/1.1543875 (3 pages) | Cited 8 times

Online Publication Date: 9 May 2003

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By tuning the incidence angle of hard, circularly polarized x-rays with respect to the sample surface, we are able to independently probe surface and bulk magnetic states in a Fe(35 Å)[Gd(50 Å)/Fe(35 Å)]15 ferrimagnetic multilayer by magnetic circular dichroism (MCD). We show that a twisted magnetic state nucleates at the surface of the multilayer at T≈0.7 Tcomp, where Tcomp is the ferrimagnetic compensation temperature. At nucleation, the twist penetrates ≈170 Å or two bilayers. Despite its theoretical prediction by LePage and Camley more than 15 years ago [J. G. LePage and R. E. Camley, Phys. Rev. Lett. 65, 1152 (1990); R. E. Camley, Phys. Rev. B 35, 3608 (1987)], this surface-twisted state has eluded direct experimental detection up to now. Its clear observation here demonstrates the power of grazing incidence, hard x-ray, MCD measurements for studies of magnetic phase transitions in layered structures. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.20.Ls Magneto-optical effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Gg Ferrimagnetics

Resonant magnetic x-ray and neutron diffuse studies of transition metal multilayers

T. P. A. Hase, J. D. R. Buchanan, B. K. Tanner, S. Langridge, R. M. Dalgliesh, S. Foster, C. H. Marrows, and B. J. Hickey

J. Appl. Phys. 93, 6510 (2003); http://dx.doi.org/10.1063/1.1543876 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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Electron scattering mechanisms within metallic multilayers are affected by both structural and magnetic disorders. Off-specular x-ray scattering has long been used to probe the structural interfaces, and it is only recently that it has been applied to the study of magnetic disorder. We compare the resonant magnetic x-ray scattering with off-specular neutron studies from magnetron-sputtered Co/Cu and Co/Ru multilayers grown at the second antiferromagnetic coupling peak. Both techniques yield similar results for the Cu system, and a simple domain model can be applied to extract the magnetic interface morphological parameters. For the Cu system, the in-plane correlation length is field dependent and is 880±20 Å after saturation along the hard axis, but increases to 7000±100 Å after saturation along the orthogonal easy axis. Both systems show strong out-of-plane correlations in both the structural and magnetic disorders. In all cases, the out-of-plane correlation length for the structural interfaces is 200–250 Å, but the ratio of the magnetic to structural correlations length is dependent on the magnitude of the exchange coupling and ranges from 0.4 to 1.4. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.70.Ck X-ray scattering
68.35.Ct Interface structure and roughness
75.50.Cc Other ferromagnetic metals and alloys
75.30.Et Exchange and superexchange interactions
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance

Body centered cubic buffer layers for enhanced lateral grain growth of Co/Cu multilayers

Masakiyo Tsunoda, Daisuke Takahashi, and Migaku Takahashi

J. Appl. Phys. 93, 6513 (2003); http://dx.doi.org/10.1063/1.1543877 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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The effect of buffer layers (BLs) on metallurgical microstructure and giant magnetoresistance of Co/Cu multilayers fabricated on them is discussed. The lateral grain size and the magnetoresistance (MR) ratio of multilayers are generally enlarged with changing the chemical composition of BLs toward a limiting concentration, within the range where the solid solution of body-centered-cubic (bcc) structure is formed. A guiding principle for material research for the BLs, which realize flat interfaces with large lateral grain size in the multilayers, is deduced from the correlation between the MR ratio of the multilayers and the surface energy of bcc BLs: the difference between the surface energy of BL (γS) and the interfacial energy (γSL) in Young–Dupré’s equation (cos θ=(γS−γSL)/γL) should agree with the surface energy of Co layer (γL), which is deposited first on the BL. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Cc Other ferromagnetic metals and alloys
75.47.De Giant magnetoresistance
68.55.A- Nucleation and growth
68.35.Md Surface thermodynamics, surface energies

Soft x-ray longitudinal magneto-optical Kerr effect measured from Co/Cu multilayers at the Co L2,3 edges

M. Hecker, H.-C. Mertins, D. Abramsohn, W. Gudat, and C. M. Schneider

J. Appl. Phys. 93, 6516 (2003); http://dx.doi.org/10.1063/1.1555320 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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We report on x-ray magneto-optical reflectivity investigations of Co/Cu multilayers with circularly polarized synchrotron light. The individual layer thicknesses of the samples were tuned to the second maximum of the giant magnetoresistance. An external magnetic field was applied parallel to the sample surface and the scattering plane utilizing the longitudinal magneto-optical Kerr effect. The reflectometry curves measured at the Co L3 absorption edge clearly show antiferromagnetic (AFM) coupling of the Co layers by half-integer-order Bragg peaks of magnetic origin, which disappear for nonresonant excitation. Whereas the first-order magnetic peak overlaps with strong charge scattering contributions, the higher-order magnetic peaks are more pronounced and sensitive to magnetic effects. In an applied field, the magnetic peaks are suppressed due to a reduction of the AFM layer coupling, and an additional intensity modulation occurs due to asymmetry effects. Measurements of the photon energy dependence of the Bragg peak positions were employed close to the Co L2,3 edges to determine the dispersive part of the magneto-optical constants of the Co/Cu multilayer. © 2003 American Institute of Physics.
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78.66.Bz Metals and metallic alloys
78.20.Ls Magneto-optical effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.47.De Giant magnetoresistance
75.50.Cc Other ferromagnetic metals and alloys

Resonant magnetic reflectivity from U/Fe multilayers

S. D. Brown, A. Beesley, A. Herring, D. Mannix, M. F. Thomas, P. Thompson, L. Bouchenoire, S. Langridge, G. H. Lander, W. G. Stirling, A. Mirone, R. C. C. Ward, M. R. Wells, and S. W. Zochowski

J. Appl. Phys. 93, 6519 (2003); http://dx.doi.org/10.1063/1.1558608 (3 pages) | Cited 6 times

Online Publication Date: 9 May 2003

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U/Fe multilayers have been produced through dc sputtering. The high quality of these multilayers has been confirmed through x-ray reflectivity measurements and fitting to the resultant spectra. These samples are currently the subject of investigations using techniques including polarized neutron reflectivity, conversion electron Mössbauer spectroscopy, and magnetotransport and magneto-optic measurements. In this article, we report on results obtained from a [U 30 Å/Fe 40 Å]×30 multilayer through resonant magnetic scattering performed on the XMaS beamline at the European Synchrotron Radiation Facility. The asymmetry ratio is defined as (I+−I−)/(I++I−), where I+(I−) is the normalized intensity obtained with circular polarization and the applied field parallel (antiparallel) to the beam direction. Asymmetry data are presented as functions of both energy and momentum transfer. We have identified a Uranium moment with the use of resonant magnetic reflectivity at 12 K. Reversal of the polarity of the asymmetry ratio between the first and second superlattice peaks indicates a nonuniform moment distribution through the uranium layers. Temperature dependence measurements confirm that the moment also exists at room temperature. © 2003 American Institute of Physics.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
75.50.Ss Magnetic recording materials
75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions
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