Scanning electron microscopy with polarization analysis studies of Ni-Fe magnetic memory elements

Unguris, John; Scheinfein, M. R.; Celotta, Robert; Pierce, Daniel T.

doi:10.1109/20.42569

Cited by 6 publications

(2 citation statements)

References 6 publications

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“…Measurements of the oscillatory exchange coupling in Fe/ Ag/Fe͑001͒ trilayers 10 show not only the long-period but even the short-period oscillation, which proves that near perfect coherence of electron wave functions can be achieved in this system for Ag interlayers as thick as 50 atomic planes. 10 These experiments also show that fcc Ag grows well on bcc Fe because of the small lateral mismatch to the Fe lattice. Similarly, the mismatch to the MgO rocksalt structure is also small.…”

Section: Theoretical Formulationmentioning

confidence: 67%

Theory of resonant spin-dependent tunneling in an Fe/Ag/MgO/Fe(001) junction

2009

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Calculation of the tunneling magnetoresistance ͑TMR͒ of an Fe/Ag/MgO/Fe͑001͒ magnetic junction is reported. The magnetoresistance is determined without any approximations from the real-space Kubo formula using tight-binding bands fitted to an ab initio band structure. It is shown that the calculated TMR oscillates as a function of Ag interlayer thickness between positive values in excess of 2000% and negative values of the order of −100%. The oscillation period is determined by the spanning vector of the Ag Fermi surface. The large positive TMR and the changes in its sign are due to resonant enhancement of the tunneling conductance of majority-spin carriers in the ferromagnetic configuration and of the conductance of carriers tunneling in the antiferromagnetic configuration from the minority-spin channel in the Fe electrode adjacent to the Ag layer to the majority-spin channel in the other Fe electrode. The resonant enhancement occurs because the Ag interlayer creates potential steps for electrons in both the ferromagnetic and antiferromagnetic configurations of the junction. This mechanism, which results in a very large TMR, is quite different from the mechanism that causes large TMR in the standard Fe/MgO/Fe͑001͒. It offers the possibility of tuning the magnitude and sign of the TMR by the choice of the interlayer thickness. A Lateral supercell method was also used to investigate the effect of interfacial roughness on the resonant tunneling in an Fe/Ag/MgO/Fe͑001͒ junction. It is found that, in contrast to the Fe/MgO/Fe͑001͒ junction whose TMR is reduced drastically by disorder, the junction with a silver interlayer is much less affected by interfacial roughness.

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Section: Theoretical Formulationmentioning

confidence: 67%

Theory of resonant spin-dependent tunneling in an Fe/Ag/MgO/Fe(001) junction

2009

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“…For Au/Fe, the ratio of the strengths for the two periods happens to be close to the experimentally determined ratio of 2.1, 16 but for Ag/Fe the ratio is very far from the experimental ratio of 1.0. 17 All the coupling strengths are roughly an order of magnitude larger than measured values. 18 The Cu/Co systems have been extensively studied experimentally 19 and theoretically.…”

Section: Oscillatory Exchange Couplingmentioning

confidence: 68%

Spin-dependent interface transmission and reflection in magnetic multilayers (invited)

Stiles

1996

Journal of Applied Physics

138

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First-principles calculations of transmission and reflection from Ag/Fe, Au/Fe, Cu/Co, and Cu/Ni interfaces show very strong spin dependence that differs significantly from expectations based on free electron approximations. The results can be used to understand both the giant magnetoresistance and the oscillatory exchange coupling observed in magnetic multilayers of these materials. The spin dependence of the reflection probabilities is strong enough to give a large giant magnetoresistance even if there is no spin-dependent defect scattering. The calculated reflection amplitudes determine the strength of the oscillatory exchange coupling. ͓S0021-8979͑96͒79608-8͔

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Magnetic microstructure of the (0001) surface of hcp cobalt

Unguris

Scheinfein

Celotta

et al. 1989

Applied Physics Letters

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The magnetic domain structure of the (0001) surface of a hcp cobalt crystal was investigated using scanning electron microscopy with polarization analysis (SEMPA). This is the first observation by SEMPA of both out-of-plane and in-plane magnetization components. The perpendicular magnetization imaged with SEMPA showed a branched structure very similar to that previously observed by magneto-optic Kerr microscopy. In addition, a previously unobserved in-plane magnetic substructure was measured. The in-plane magnetization is divided into well-defined submicron domains that appear to reflect the sixfold symmetry of the crystal surface.

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Scanning electron microscopy with polarization analysis studies of Ni-Fe magnetic memory elements

Cited by 6 publications

References 6 publications

Theory of resonant spin-dependent tunneling in an Fe/Ag/MgO/Fe(001) junction

Theory of resonant spin-dependent tunneling in an Fe/Ag/MgO/Fe(001) junction

Spin-dependent interface transmission and reflection in magnetic multilayers (invited)

Magnetic microstructure of the (0001) surface of hcp cobalt

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