Oscillatory biquadratic coupling in Fe/Cr/Fe(001)

Ives, A. J. R.; Bland, J. A. C.; Hicken, R. J.; Daboo, C.

doi:10.1103/physrevb.55.12428

Cited by 13 publications

(10 citation statements)

References 35 publications

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“…Recently, Bruno [4] and Stiles [5] have shown that the coupling can be described in terms of the quantum interference due to spin dependent reflections of Bloch waves at the interfaces. The interest in this subject continues to grow as evidenced by several recent papers [6][7][8][9][10][11][12][13], which cover interesting issues such as the effect of cap layer, ordering in alloy layers, quantum oscillations of spin density, etc.…”

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“…The growth optimization will be reported separately [16]. Superlattices (50 periods) with magnetic layer of fixed thickness (t Fe 3 O 4 40 Å) and changing metallic spacer thicknesses (t TiN 5,6,8,10,12,14,16,18,20, and 24 Å) were deposited. These were then studied using x-ray diffraction, high resolution and cross-sectional transmission electron microscopy (TEM), atomic force microscopy (AFM), Rutherford backscattering (RBS), vibrating sample magnetometry, SQUID magnetometry, and four probe resistivity with and without an applied magnetic field.…”

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Oscillatory Exchange Coupling and Giant Positive Magnetoresistance inTiN/Fe3O4Superlattices

Orozco

Ogale

et al. 1999

Phys. Rev. Lett.

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Oscillatory exchange coupling is observed in TiN͞Fe 3 O 4 superlattices over length scales comparable to metallic superlattices. However, the strength of the coupling is almost an order of magnitude stronger than that commonly observed in metallic superlattices. In addition, a unique positive magnetoresistance effect is also seen. These observations are discussed in terms of the carrier confinement effects caused by the half metallicity of the magnetic layers. PACS numbers: 75.70.Cn, 75.30.Et The exchange coupling between two magnetic layers separated by a thin nonmagnetic layer is seen to oscillate as a function of the thickness of nonmagnetic layer and the oscillation amplitude is seen to damp with increasing thickness [1]. Initial attempts to explain this phenomenon using free electron RKKY-type models predicted periods of oscillation ഠp͞k F , much shorter than the commonly observed periods (ഠ10 Å) [2]. Subsequent work brought out the fact that the discrete nature of the variable spacer thickness leads to long periods due to aliasing. It is now accepted that the oscillation periods are determined by the extremal Fermi surface spanning vectors (connecting critical points on the spacer layer Fermi surface), while the properties of magnetic layers mainly influence the amplitudes and phases of the oscillations [3]. Recently, Bruno [4] and Stiles [5] have shown that the coupling can be described in terms of the quantum interference due to spin dependent reflections of Bloch waves at the interfaces. The interest in this subject continues to grow as evidenced by several recent papers [6-13], which cover interesting issues such as the effect of cap layer, ordering in alloy layers, quantum oscillations of spin density, etc.Interestingly, the entire research on oscillatory coupling is thus far concentrated only upon pure metals or metal alloys. As is well known, oxides display a very broad range of electrical properties from insulating to superconducting. The magnetic phenomena in oxides also have several facets, with the underlying mechanisms covering direct exchange, superexchange, and double exchange. There is also a wide variety of half metallic oxides such as the manganites, magnetites, molybdates, rhenites, etc., where 100% spin polarization is seen at Fermi level. In spite of such richness of available property space, it is surprising that hardly any studies have yet been reported on oscillatory exchange coupling in heterostructures based on oxides or other compounds. One possible cause for this may be the difficulties encountered in realizing perfect interfaces of defect-free ultrathin films of dissimilar systems of oxides or other compounds. Indeed, all previous attempts at observing oscillatory coupling in compounds have failed [14,15]. In this work, we demonstrate for the first time that oscillatory exchange coupling effects can be realized in magnetic oxide based heterostructures, provided superlattices (SL) with high quality interfaces can be grown. We also observe an entirely unique giant positive magne...

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Oscillatory Exchange Coupling and Giant Positive Magnetoresistance inTiN/Fe3O4Superlattices

Orozco

Ogale

et al. 1999

Phys. Rev. Lett.

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“…[4][5][6] One of the most-studied systems is Fe/Cr, because they exhibit interesting properties like the magnetic interlayer exchange coupling, 3 the giant magnetoresistance 7 and the variable magnitude of the Cr moment. 8 Several experiments have detected these particular properties -polar Kerr measurements in Fe/Cr/Fe (001), 9 Mössbauer spectroscopy. 8 On the other hand, several theoretical calculations exist in the scientific literature where these anomalies are predicted in low-dimensional systems with Fe and Cr 4 and in Cr N clusters embedded in bulk Fe.…”

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LOCAL MAGNETIC MOMENTS OF Fe₁/Cr_N NANOINCLUSIONS EMBEDDED IN BULK Fe

2002

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Local magnetic moments of Fe1/CrN inclusions in an Fe matrix are calculated as a function of the Cr number of atoms N at zero temperature, and for N ≤ 64. We use a realistic spd-band Hamiltonian to determine their magnetic properties. The local magnetic moments µ(i) at the various cluster sites i are calculated self-consistently in the unrestricted Hartree-Fock approximation. The matrix Fe atoms couple always antiferromagnetically with the Cr atoms. The µ(i) of Cr atoms at the interface are enhanced by the presence of Fe atoms in their first nearest neighbor shell. In most cases the Fe moments close to the cluster are reduced. A remarkable interplay between the antiferromagnetism of Cr and the ferromagnetism of Fe is obtained.

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“…Another possible origin of the oscillatory magnetic anisotropy may be biquadratic exchange coupling. 17 Biquadratic coupling could be effective when bilinear coupling diminishes due to interface roughness.…”

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