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Maat, S.; Zeltser, A.; Li, J.; Nix, L.; Gurney, B. A.

doi:10.1103/physrevb.70.014434

Cited by 5 publications

(2 citation statements)

References 17 publications

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“…al. [22] measured a value for ψ ′ 1 in almost exact agreement with that predicted by the calculation of Ref. [18], providing strong evidence for the existence of the effect described here.…”

Section: ω(N) ∝supporting

confidence: 88%

Topological phase of the interlayer exchange coupling with application to magnetic switching

Umerski¹

2017

Preprint

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We show, theoretically, that the phase of the interlayer exchange coupling (IEC) undergoes a topological change of approximately 2π as the chemical potential of the ferromagnetic (FM) lead moves across a hybridization gap (HG). The effect is largely independent of the detailed parameters of the system, in particular the width of the gap. The implication is that for a narrow gap, a small perturbation in the chemical potential of the lead can give a sign reversal of the exchange coupling. This offers the possibility of controlling magnetization switching in spintronic devices such as MRAM, with little power consumption. Furthermore we believe that this effect has already been indirectly observed, in existing measurements of the IEC as a function of temperature and of doping of the leads.

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Section: ω(N) ∝supporting

confidence: 88%

Topological phase of the interlayer exchange coupling with application to magnetic switching

Umerski¹

2017

Preprint

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“…It is necessary to account for the significant self-heating in these low-specific-resistance MTJs, which varies as [25] T=5.6 K coercive field for sample 1 for the change in saturation magnetization (M s ) between 5.6 K and room temperature (RT) [26]. Assuming that the critical currents and β are the same in region 2 as in region 1, we obtain E a = 0.53±0.01 eV and H c,o = 285±10 Oe, where the latter is also in excellent agreement with the other coercive field determined from the low T measurement, H c,0 = 282±10 Oe.…”

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confidence: 99%

Spin Torque, Tunnel-Current Spin Polarization, and Magnetoresistance in MgO Magnetic Tunnel Junctions

et al. 2006

Phys. Rev. Lett.

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We examine the spin torque (ST) response of magnetic tunnel junctions (MTJs) with ultra-thin MgO tunnel barrier layers to investigate the relationship between the spin-transfer torque and the tunnel magnetoresistance (TMR) under finite bias. We find that the spin torque per unit current exerted on the free layer decreases by less than 10% over a bias range where the TMR decreases by over 40%. We examine the implications of this result for various spin-polarized tunneling models and find that it is consistent with magnetic-state-dependent effective tunnel decay lengths. 75.75.+a, The ability of electron currents to transfer spin angular momentum, as well as charge, from one ferromagnetic electrode to another, and hence to exert a significant spintorque on the electrodes (see e.g. refs. 1, 2), provides a powerful new tool for the study of spin transport in electronic structures, in addition to establishing new opportunities for future applications [2,3]. The closely related issue of spin-dependent electron transport in magnetic multilayer structures, both magnetic tunnel junctions (MTJs) [4] and spin valves [5], is of wide-spread interest, both fundamentally and because the importance this phenomena has for information storage [6,7]. A critical aspect of MTJs is the bias dependence of the tunnel magnetoresistance (TMR) [see e.g. ref. 8], which in general, decreases as the voltage bias (V) increases. Currently, there is no consensus as to a microscopic model that accounts for this behavior. Here we report our study of the relationship between bias dependent TMR and spintransfer torque, which is fundamental to understanding both the nature of spin-polarized tunneling at finite bias and spin transfer effects in MTJs [9,10,11]. By making measurements of the thermally activated switching of nanostructured MTJs, we determine the bias dependence of the spin-torque transferred across an MgO tunnel barrier and its relation to the TMR. The spin-torque per unit current is, within 10%, a constant function of V up to ±0.35 V in our devices, in contrast to the TMR which is reduced by >40% at ±0.35 V . This behavior is inconsistent with a decrease in the tunnel polarization factors of the electrodes as described by free-electron tunneling models [12,13,14], or by surface-magnon emission models that substantially decrease the surface magnetization with increasing bias [15]. We find, however, that magneticstate-dependent tunneling decay lengths (effective masses) as theoretically predicted to result in very high TMR in MgO tunnel barriers [16,17,18], are consistent with our results, if we include the effects of our ultra-thin barrier layers having a high density of atomic defects and lower barrier heights than ideal MgO barriers.

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Magnetoresistance and Spin Valves

2008

From Bulk to Nano

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Evidence for weak electron confinement in spin valves havingCo90Fe10∕Cu∕Co90Fe<

Cited by 5 publications

References 17 publications

Topological phase of the interlayer exchange coupling with application to magnetic switching

Topological phase of the interlayer exchange coupling with application to magnetic switching

Spin Torque, Tunnel-Current Spin Polarization, and Magnetoresistance in MgO Magnetic Tunnel Junctions

Magnetoresistance and Spin Valves

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