Search results for "permalloy"
showing 10 items of 28 documents
Domain-wall induced large magnetoresistance effects at zero applied field in ballistic nanocontacts
2013
We determine magnetoresistance effects in stable and clean Permalloy nanocontacts of variable cross section, fabricated by UHV deposition and in situ electromigration. To ascertain the magnetoresistance (MR) effects originating from a magnetic domain wall, we measure the resistance values with and without such a wall at zero applied field. In the ballistic transport regime, the MR ratio reaches up to 50% and exhibits a previously unobserved sign change. Our results can be reproduced by recent atomistic calculations for different atomic configurations of the nanocontact, highlighting the importance of the detailed atomic arrangement for the MR effect. DOI: 10.1103/PhysRevLett.110.067203
Importance of spin current generation and detection by spin injection and the spin Hall effect for lateral spin valve performance.
2018
Lateral spin valves are attractive device geometries where functional spin currents can be generated and detected by various mechanisms, such as spin injection and the direct and the inverse spin Hall effect. To understand the mechanisms behind these effects better, as well as their potential for application in devices, we combine multiple mechanisms in multi-terminal Pt-Py-Cu lateral spin valves: we generate pure spin currents in the copper spin conduit both via the spin Hall effect in platinum and electric spin injection from permalloy and detect signals both via conventional non-local detection and via the inverse spin Hall effect in the same device at variable temperatures. Differences …
Emergence of the stripe-domain phase in patterned permalloy films
2016
The occurrence of stripe domains in ferromagnetic Permalloy (Py=Fe$_{20}$Ni$_{80}$) is a well known phenomenon which has been extensively observed and characterized. This peculiar magnetic configuration appears only in films with a thickness above a critical value ($d_{cr}$), which is strongly determined by the sputtering conditions (i.e. deposition rate, temperature, magnetic field). So far, $d_{cr}$ has usually been presented as the boundary between the homogeneous (H) and stripe-domains (SD) regime, respectively below and above $d_{cr}$. In this work we study the transition from the H to the SD regime in thin films and microstructured bridges of Py with different thicknesses. We find the…
Scaling of intrinsic domain wall magneto-resistance with confinement in electromigrated nanocontacts
2018
In this work we study the evolution of intrinsic domain wall magnetoresistance (DWMR) with domain wall confinement. Clean permalloy notched half-ring nanocontacts are fabricated using a special ultra-high vacuum electromigration procedure to tailor the size of the wire in-situ and through the resulting domain wall confinement we tailor the domain wall width from a few tens of nm down to a few nm. Through measurements of the dependence of the resistance with respect to the applied field direction we extract the contribution of a single domain wall to the MR of the device, as a function of the domain wall width in the confining potential at the notch. In this size range, an intrinsic positive…
Ab-initio Calculation of the Properties of Permalloys Used in Electrical Machines
2006
In this paper an ab-initio calculation that allows to describe the main features of permalloys is presented. The calculation is bawd on Korringa-Kohn-Rostoker electronic structure method. The dependence of the magnetocryttalline anisotropy and of the magnetostriction on the concentration of non magnetic addiction is computed.
Tuning Spin Current Injection at Ferromagnet-Nonmagnet Interfaces by Molecular Design.
2020
There is a growing interest in utilizing the distinctive material properties of organic semiconductors for spintronic applications. Here, we explore the injection of pure spin current from Permalloy into a small molecule system based on dinaphtho[2,3-b:2,3-f]thieno[3,2-b]thiophene (DNTT) at ferromagnetic resonance. The unique tunability of organic materials by molecular design allows us to study the impact of interfacial properties on the spin injection efficiency systematically. We show that both the spin injection efficiency at the interface and the spin diffusion length can be tuned sensitively by the interfacial molecular structure and side chain substitution of the molecule.
Direct observation of spin diffusion enhanced nonadiabatic spin torque effects in rare-earth-doped permalloy
2018
The relation between the nonadiabaticity parameter $\ensuremath{\beta}$ and the damping parameter $\ensuremath{\alpha}$ is investigated in permalloy-based microdisks. In order to determine $\ensuremath{\beta}$, high-resolution imaging of the current-induced vortex-core displacement is performed using scanning electron microscopy with polarization analysis. The materials properties of the films are varied via rare-earth Dy doping, leading to a greatly enhanced damping, while retaining the same spin configuration for the confined vortex state. A clear trend to much higher nonadiabaticity values is seen for the higher doping levels and an averaged value of $\ensuremath{\beta}=(0.29\ifmmode\pm\…
Staggered magnetic nanowire devices for effective domain-wall pinning in racetrack memory
2019
Domain-wall memory devices, in which the information is stored in nanowires, are expected to replace hard disk drives. A problem that remains to be solved in domain-wall memory is to pin the domain walls in a controllable manner at the nanometer scale using simple fabrication. We demonstrate the possibility to stabilize domain walls by making staggered nanowires. Controllable domain-wall movement is exhibited in permalloy nanowires using magnetic fields where the pinning field is about 10 mT. The pinning field and stability of the domain walls can be increased by adjusting the offset dimensions of the staggered nanowires. Domain-wall velocities of about 200 m/s are computed for the experime…
Stroboscopic XMCD–PEEM imaging of standing and propagating spinwave modes in permalloy thin-film structures
2007
Abstract Using synchrotron-based stroboscopic photoemission electron microscopy with X-ray circular dichroism as contrast method, we have investigated the high-frequency response of permalloy thin-film structures. Standing precessional modes have been studied in rectangular elements (16 × 32 μm 2 , 10 nm thick) with a high time resolution of about 15 ps in the low- α mode of BESSY. With increasing amplitude of the applied magnetic AC field the particle is driven from an initial symmetric Landau flux-closure state into an asymmetric state and finally into a single-domain state magnetized perpendicular to the applied field H AC . The electromagnetic microwave field thus can induces a net magn…
Self-Trapping of Magnetic Oscillation Modes in Landau Flux-Closure Structures
2005
We investigated the magnetodynamics in rectangular Permalloy platelets by means of time-resolved x-ray photoemission microscopy. 10 nm thick platelets of size 16 x 32 microm were excited by an oscillatory field along the short side of the sample with a fundamental frequency of 500 MHz and considerable contributions of higher harmonics. Under the influence of the oscillatory field, the Néel wall in the initial classical Landau pattern shifts away from the center, corresponding to an induced magnetic moment perpendicular to the exciting field. This phenomenon is explained by a self-trapping effect of the dominating spin-wave mode when the system is excited just below the resonance frequency. …