Search results for "mesoscale and nanoscale physics"
showing 10 items of 720 documents
The promise of spintronics for unconventional computing
2021
Novel computational paradigms may provide the blueprint to help solving the time and energy limitations that we face with our modern computers, and provide solutions to complex problems more efficiently (with reduced time, power consumption and/or less device footprint) than is currently possible with standard approaches. Spintronics offers a promising basis for the development of efficient devices and unconventional operations for at least three main reasons: (i) the low-power requirements of spin-based devices, i.e., requiring no standby power for operation and the possibility to write information with small dynamic energy dissipation, (ii) the strong nonlinearity, time nonlocality, and/o…
A random-walk benchmark for single-electron circuits
2021
Mesoscopic integrated circuits aim for precise control over elementary quantum systems. However, as fidelities improve, the increasingly rare errors and component crosstalk pose a challenge for validating error models and quantifying accuracy of circuit performance. Here we propose and implement a circuit-level benchmark that models fidelity as a random walk of an error syndrome, detected by an accumulating probe. Additionally, contributions of correlated noise, induced environmentally or by memory, are revealed as limits of achievable fidelity by statistical consistency analysis of the full distribution of error counts. Applying this methodology to a high-fidelity implementation of on-dema…
Magnetic sensitivity distribution of Hall devices in antiferromagnetic switching experiments
2021
We analyze the complex impact of the local magnetic spin texture on the transverse Hall-type voltage in device structures utilized to measure magnetoresistance effects. We find a highly localized and asymmetric magnetic sensitivity in the eight-terminal geometries that are frequently used in current-induced switching experiments, for instance to probe antiferromagnetic materials. Using current-induced switching of antiferromagnetic NiO/Pt as an example, we estimate the change in the spin Hall magnetoresistance signal associated with switching events based on the domain switching patterns observed via direct imaging. This estimate correlates with the actual electrical data after subtraction …
Optical read-out of the N\'eel vector in metallic antiferromagnet Mn$_{2}$Au
2021
Metallic antiferromagnets with broken inversion symmetry on the two sublattices, strong spin-orbit coupling and high N\'{e}el temperatures offer new opportunities for applications in spintronics. Especially Mn$_{2}$Au, with high N\'{e}el temperature and conductivity, is particularly interesting for real-world applications. Here, manipulation of the orientation of the staggered magnetization,\textit{\ i.e.} the N\'{e}el vector, by current pulses has been recently demonstrated, with the read-out limited to studies of anisotropic magnetoresistance or X-ray magnetic linear dichroism. Here, we report on the in-plane reflectivity anisotropy of Mn$_{2}$Au (001) films, which were N\'{e}el vector al…
On the role of the nonlocal Hartree-Fock exchange in ab initio quantum transport: Hydrogen in Platinum nanocontacts revisited
2008
We propose a practical way to overcome the ubiquitous problem of the overestimation of the zero-bias and zero-temperature conductance, which is associated to the use of local approximations to the exchange-correlation functional in Density-Functional Theory when applied to quantum transport. This is done through partial substitution of the local exchange term in the functional by the nonlocal Hartree-Fock exchange. As a non-trivial example of this effect we revisit the smallest molecular bridge studied so far: a Hydrogen molecule placed in between Platinum nanocontacts. When applied to this system the value of the conductance diminishes as compared to the local-exchange-only value, which is…
Electronic charge redistribution in LaAlO$_3$(001) thin films deposited at SrTiO$_3$(001) substrate: First principles analysis and the role of stoich…
2012
We present a comprehensive first-principles study of the electronic charge redistribution in atomically sharp LaAlO$_3$/SrTiO$_3$(001) heterointerfaces of both n- and p-types allowing for non-stoichiometric composition. Using two different computational methods within the framework of the density functional theory (linear combination of atomic orbitals and plane waves) we demonstrate that conducting properties of LaAlO$_3$/SrTiO$_3$(001) heterointerfaces strongly depend on termination of LaAlO$_3$ (001) surface. We argue that both the polar "catastrophe" and the polar distortion scenarios may be realized depending on the interface stoichiometry. Our calculations predict that heterointerface…
Mechanism of electrical switching of ultra-thin CoO/Pt bilayers
2023
We study current-induced switching of the N\'eel vector in CoO/Pt bilayers to understand the underlaying antiferromagnetic switching mechanism. Surprisingly, we find that for ultra-thin CoO/Pt bilayers electrical pulses along the same path can lead to an increase or decrease of the spin Hall magnetoresistance signal, depending on the current density of the pulse. By comparing the results of these electrical measurements to XMLD-PEEM imaging of the antiferromagnetic domain structure before and after the application of current pulses, we reveal the reorientation of the N\'eel vector in ultra-thin CoO(4 nm). This allows us to determine that even opposite resistance changes can result from a th…
Multiscale simulations of topological transformations in magnetic Skyrmions
2017
Magnetic Skyrmions belong to the most interesting spin structures for the development of future information technology as they have been predicted to be topologically protected. To quantify their stability, we use an innovative multiscale approach to simulating spin dynamics based on the Landau-Lifshitz-Gilbert equation. The multiscale approach overcomes the micromagnetic limitations that have hindered realistic studies using conventional techniques. We first demonstrate how the stability of a Skyrmion is influenced by the refinement of the computational mesh and reveal that conventionally employed traditional micromagnetic simulations are inadequate for this task. Furthermore, we determine…
Thickness and power dependence of the spin-pumping effect in Y3Fe5O12/Pt heterostructures measured by the inverse spin Hall effect
2013
The dependence of the spin-pumping effect on the yttrium iron garnet (Y3Fe5O12, YIG) thickness detected by the inverse spin Hall effect (ISHE) has been investigated quantitatively. Due to the spin-pumping effect driven by the magnetization precession in the ferrimagnetic insulator YIG film a spin-polarized electron current is injected into the Pt layer. This spin current is transformed into electrical charge current by means of the ISHE. An increase of the ISHE-voltage with increasing film thickness is observed and compared to the theoretically expected behavior. The effective damping parameter of the YIG/Pt samples is found to be enhanced with decreasing YIG film thickness. The investigate…
Coupling of ferromagnetic and antiferromagnetic spin dynamics in Mn$_{2}$Au/NiFe thin-film bilayers
2023
We investigate magnetization dynamics of Mn$_{2}$Au/Py (Ni$_{80}$Fe$_{20}$) thin film bilayers using broadband ferromagnetic resonance (FMR) and Brillouin light scattering spectroscopy. Our bilayers exhibit two resonant modes with zero-field frequencies up to almost 40 GHz, far above the single-layer Py FMR. Our model calculations attribute these modes to the coupling of the Py FMR and the two antiferromagnetic resonance (AFMR) modes of Mn2Au. The coupling-strength is in the order of 1.6 T$\cdot$nm at room temperature for nm-thick Py. Our model reveals the dependence of the hybrid modes on the AFMR frequencies and interfacial coupling as well as the evanescent character of the spin waves th…