The interfacial Dzyaloshinskii-Moriya interaction (DMI) plays a crucial role in chiral domain wall (DW) motion, favoring fast DW velocities. We explore the effect of interface disorder on DMI and dynamics perpendicular magnetized Ta/CoFeB/MgO thin films. Light ${\mathrm{He}}^{+}$ irradiation has been used to gently engineer intermixing scale 0.1 nm. demonstrate that slight modification Ta/CoFeB leads an increase value accompanied by enhancement velocity flow regime. Using micromagnetic...

The gyrotropic rotation around the equilibrium position constitutes fundamental excitation of magnetic vortices in nanostructures. frequency this mode varies with material and sample geometry, but is independent vortex handedness its core direction. Here, we demonstrate that degeneracy lifted a spin-torque oscillator containing two stacked on top each other. When driven by spin-polarized currents, such devices exhibit set dynamic modes discretely split frequencies, corresponding to specific...

Thin films of perovskite oxides offer the possibility combining emerging concepts strongly correlated electron phenomena and spin current in magnetic devices. However, transport magnetization dynamics these complex oxide materials are not well understood. Here, we experimentally quantify parameters damping epitaxial ferromagnet/paramagnet bilayers ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{MnO}}_{3}/{\mathrm{SrRuO}}_{3}$ (LSMO/SRO) by broadband ferromagnetic resonance spectroscopy. From...

Excited magnetization dynamics in a spin-valve device consisting of an in-plane polarizer and out-of-plane free layer were studied numerically. In the case where is assumed to lack any anisotropy components, finite external field required generate steady-state dynamics, agreement with previous reports. We demonstrate that this constraint can be removed precession stabilized zero applied by introducing additional axis. Moreover, offers degree freedom for tuning frequency response device.

Interlayer exchange coupling between layers with perpendicular and easy-plane magnetic anisotropies separated by a non-magnetic spacer is studied using ferromagnetic resonance. The samples consist of Co/Ni multilayer anisotropy CoFeB layer variable thickness Ru layer. At fixed frequency, we show that there an avoided crossing resonance modes providing direct evidence for interlayer coupling. mode dispersions different thicknesses are fit to Heisenberg-type model determine the strength...

We report on the experimental and analytical work spin-transfer torque induced vortex dynamics in metallic nanopillars with in-plane magnetized layers. study a diameter of 150 nm, containing two Fe layers thickness 15 nm 30 respectively, separated by 6 Ag spacer. The sample geometry is such that it allows for formation magnetic vortices discs. As confirmed micromagnetic simulations, we are able to prepare states where one layer homogeneously while other contains vortex. experimentally show...

The static and dynamic magnetic properties of tetragonally distorted Mn--Ga based alloys were investigated. Static are determined in fields up to 6.5~T using SQUID magnetometry. For the pure Mn$_{1.6}$Ga film, saturation magnetisation is 0.36~MA/m coercivity 0.29~T. Partial substitution Mn by Co results Mn$_{2.6}$Co$_{0.3}$Ga$_{1.1}$. those films drops 0.2~MA/m increased 1~T. Time-resolved magneto-optical Kerr effect (TR-MOKE) used probe high-frequency dynamics Mn--Ga. ferromagnetic...

We calculate the switching voltages for MgO-based magnetic tunnel junctions taking into account both in-plane and fieldlike spin-torque terms. To this end, we analytically solve Landau-Lifshitz-Gilbert equation a generalized geometry. assume that varies linearly with applied voltage, while torque exhibits quadratic voltage dependence. Specifically, consider free layer has two generic, orthogonal anisotropy components, one of which is along direction defined by magnetization reference layer,...

We present a combined analytical and numerical study on double-vortex spin-torque nano-oscillators describe mechanism that suppresses the windmill modes. The magnetization dynamics is dominated by gyrotropic precession of vortex in one ferromagnetic layers. In other layer gyration strongly damped. dominating for determined current polarity. Measurements Fe/Ag/Fe nano-pillars support these findings. results open up new perspective building high quality-factor oscillators operating at...

Spin-transfer-torque-induced switching is investigated in 200 nm diameter circularly shaped, perpendicularly 10 magnetized nanopillars. A synthetic antiferromagnet, consisting of two Co/Ni multilayers coupled antiferromagnetically 11 across a Ru layer, used as reference layer to minimize the dipolar field on free layer. The single 12 4 × [Co/Ni] multilayer. use Pt and Pd was avoided lower spin-orbit scattering magnetic layers intrinsic 13 damping therefore, reduce critical current required...

We present a study of pulsed current switching characteristics spin-valve nanopillars with in-plane magnetized dilute permalloy and undiluted free layers in the ballistic regime at low temperatures. The layer device switches much faster: characteristic time for (Ni0.83Fe0.17) is 1.18 ns, while that ([Ni0.83Fe0.17]0.6Cu0.4) 0.475 ns. A macrospin model can capture data trends reduced spin-torque asymmetry parameter, spin polarization, increased Gilbert damping relative to devices. Our...

Magnetic bilayers with different magnetic anisotropy directions are interesting for spintronic appli- cations as they offer the possibility to engineer tilted remnant magnetization states. We investigate ferromagnetic resonance (FMR) linewidth of modes associated two interlayer exchange- coupled layers, first a CoNi multilayer perpendicular anisotropy, and second CoFeB layer an easy-plane anisotropy. For antiferromagnetic ex- change coupling, elevated FMR linewidths observed below...

Spin-transfer torques (STTs) can be exploited in order to manipulate the magnetic moments of nanomagnets, thus allowing for new consumer-oriented devices designed. Of particular interest here are tuneable radio-frequency (RF) oscillators wireless communication. Currently, structure that maximizes output power is an Fe/MgO/Fe-type tunnel junction (MTJ) with a fixed layer magnetized plane layers and free perpendicular plane. This allows most magnetoresistance (TMR) converted into power. Here,...

The investigation of propagating spin waves is a key topic contemporary magnetism research. For the excitation with short wavelengths, it was typically necessary to either use transducers sizes on order desired wavelengths (striplines or point-contacts) generate those parametrically by double-frequency spatially uniform microwave signal. Only recently, novel mechanism for local waves, which overcomes wavelength limit given minimum patterning size has been discovered. This method utilizes...

In antiferromagnetic materials the order parameter exhibits resonant modes at frequencies that can be in terahertz range, making them interesting components for spintronic devices. Here, it is shown resonance excited using inverse spin-Hall effect a system consisting of an insulator coupled to normal-metal waveguide. The time-dependent interplay between spin-torque, ac spin-accumulation and magnetic degrees freedom studied. It found dynamics antiferromagnet effects frequency-dependent...

We report the effect of annealing temperature on dynamic and static magnetic properties MgO/CoFeB/Ta/Ru multilayers. Angular resolved ferromagnetic resonance measurement results show that as-deposited film exhibits in-plane anisotropy, whereas in annealed films easy-axis is almost along direction perpendicular to plane layers. The extracted interfacial anisotropy energy, Ki, maximized at an 225∘C, agreement with vibrating sample magnetometry results. Although magnetization not fully...

A focused ion beam was used to obtain cross-sectional specimens from both magnetic multilayer and Nb/Al-AlOx/Nb Josephson junction devices for characterization by scanning transmission electron microscopy (STEM) energy dispersive X-ray spectroscopy (EDX). Automated multivariate statistical analysis of the EDX spectral images produced chemically unique component individual layers within structures. STEM imaging elucidated distinct variations in film morphology, interface quality, and/or etch...

Spin-torque oscillators are a promising application for the spin-transfer torque effect. The major challenge lies in pushing their microwave output power to useful levels, e.g. by operating an array of spin-torque synchronized, phase-locked mode. Our experiments on metallic, GMR-type nanopillars focus influence external high-frequency signals current-driven vortex dynamics single-vortex and double-vortex spintorque oscillators. For both cases we observe injection locking behavior according...

Here, we demonstrate numerically that shape anisotropy in MgO-based spin-torque nano-oscillators consisting of an out-of-plane magnetized free layer and in-plane polarizer is necessary to stabilize magnetization precession without the need external magnetic fields. As increased, a gradual tilting towards easy direction introduced, favouring zero-field dynamics over static states. Above critical value, are no longer observed. The optimum ratio uniaxial anisotropy, for which large angle occur...

Tunnel magnetoresistance (TMR) was measured in CoFeB–MgO-based double-barrier magnetic tunnel junctions. The variation of sputtering power density is used to control the relative B content middle electrode. MR ratios both top and bottom junctions are suppressed with respect single-barrier case. While junction shows a saturation as function high-temperature annealing for all densities, exhibits an increase temperature higher values density. suppression high attributed lack strong...

Here, we present an analytical and numerical model describing the magnetization dynamics in MgO-based spin-torque nano-oscillators with in-plane magnetized polarizer out-of-plane free layer. We introduce spin-transfer torque asymmetry by considering cosine angular dependence of resistance between two magnetic layers stack. For solution, are determined assuming a circular precession trajectory around direction perpendicular to plane, as set effective field, calculating energy integral over...

Spin-transfer-torque driven magnetization dynamics in a spin-valve device consisting of an in-plane magnetized polarizer and out-of-plane free layer were studied numerically. Such devices hold promise for nanoscale wireless transmitters operating at gigahertz frequencies, compatible with current mobile telephone local area network technologies [1]. In traditional spin-transfer-torque devices, applications as memory elements (spin-transfer-torque MRAM), the magnetic easy axes both reference...

MgO-based magnetic tunnel junctions (MTJs) are currently the structures of choice for random access memories (MRAMs), as they exhibit extremely high magnetoresistance (TMR) values due to highly effective spin-dependent tunneling [1, 2]. Initial studies focused on devices with both free and reference layers exhibiting in-plane remnant states [3, 4]. On other hand, it has been reported that having magnetized perpendicular layer interface offer a better trade-off between reducing writing power...

This paper aims to explore potential mechanisms for sustaining steady-state precession in MgO-based magnetic tunnel junctions (MTJ) with an in-plane polarizer and out-of-plane free layer. The Landau-Lifshitz-Gilbert-Slonczewski equation is analytically numerically solved a nano-pillar MTJ circular cross-section under constant perpendicular applied current field. It demonstrated that the spin torque angular asymmetry sufficient sustain transfer torque-driven dynamics of spin-torque nano-oscillators.