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We describe the effect of the Fe layer thickness on the antiferromagnetic interlayer exchange coupling in [Fe/MgO]\\(_N\\) superlattices. An increase in coupling strength with increasing Fe layer thickness is observed, which highlights the need of including the extension of both the layers when discussing the interlayer exchange coupling in superlattices.

We investigate the magnetization dynamics in nanomagnet vertices often found in artificial spin ices. Our analysis involves creating a simplified model that depicts edge magnetization using magnetic charges. We utilize the model to explore the energy landscape, its associated curvatures, and the fundamental modes. Our study uncovers specific magnonic regimes and transitions between magnetization states, marked by zero-modes, which can be understood within the framework of Landau theory. To verify our model, we compare it with micromagnetic simulations, demonstrating a noteworthy agreement.

We numerically study a mesoscopic system consisting of magnetic nanorings in the presence of thermal magnetization fluctuations. We find the formation of dipolar-field-mediated ``bonds\" promoting the formation of annuli clusters, where the amount of bonds between two rings varies between zero and two. This system resembles the formation of polymers from artificial atoms, which in our case are the annuli and where the valency of the atom is set by the ring multipolarity. We investigate the thermodynamic properties of the resulting structures, and find a transition associated with the formation of the bonds. In addition, we find that the system has a tendency to form topological structures, with a distinct critical temperature in relation to the one for bond formation.

We present a method for the additive fabrication of planar magnetic nanoarrays with minimal surface roughness. Synthesis is accomplished by combining electron-beam lithography, used to generate nanometric patterned masks, with ion implantation in thin films. By implanting \\(^{56}\\)Fe\\(^{+}\\) ions, we are able to introduce magnetic functionality in a controlled manner into continuous Pd thin films, achieving 3D spatial resolution down to a few tens of nanometers. Our results demonstrate the application of this technique in fabricating square artificial spin ice lattices, which exhibit well-defined magnetization textures and interactions among the patterned magnetic elements.

We investigate the design of magnetic ordering in one-dimensional mesoscopic magnetic Ising chains by modulating long-range interactions. These interactions are affected by geometrical modifications to the chain, which adjust the energy hierarchy and the resulting magnetic ground states. Consequently, the magnetic ordering can be tuned between antiferromagnetic and dimer antiferromagnetic phases. These phases are experimentally observed in chains fabricated using both conventional electron-beam lithography and ion implantation techniques, demonstrating the feasibility of controlling magnetic properties at the mesoscale. The ability of attaining these magnetic structures by thermal annealing, underlines the potential of using such systems instead of simulated annealers in tackling combinatorial optimization tasks.

The tuning of magnetic properties through electrochemical loading of hydrogen has recently attracted significant interest as a way to manipulate magnetic devices with electric fields. In this paper we investigate quantitatively the magneto-ionic effect of hydrogen uptake on the magnetic properties of rare-earth transition metal alloy Tb\\(_x\\)Co\\(_{(100-x)}\\) in the composition range of \\(x=10-39\\) at.\\% using ion implantation. Using this technique we are able to link changes in magnetic behaviour to exact concentrations of hydrogen, isolated from the movement of any other ions that would be a factor in electrochemical studies. The composition of the alloy has been varied alongside the hydrogen dose to characterize the effect of progressive hydrogen loading on the full range of \\(x\\) displaying out-of-plane magnetic anisotropy. We find large changes in two important properties: the compensation composition and the Co-rich in-plane to out-of-plane magnetic anisotropy transition composition, both of which move by 6 at.\\% towards higher Tb concentrations after hydrogen implantation. This shift in composition does not increase with a larger dose. From the changes in magnetization we attribute the change in compensation composition to a significant reduction of the moment on the Tb sublattice.

Spontaneous symmetry breaking is ubiquitous in physics. Its spectroscopic signature consists in the softening of a specific mode upon approaching the transition from the high symmetry side and its subsequent splitting into a zero-frequency \"Goldstone\" mode and a non-zero-frequency \"Higgs\" mode. Although they determine the whole system dynamics, these features are difficult to address in practice because of their vanishing coupling to most experimental probes and/or their strong interaction with other fluctuations. In this work, we consider a periodic magnetic modulation occurring in a ferromagnetic film with perpendicular-to-plane magnetic anisotropy and directly observe its Goldstone and Higgs spin-wave modes at room temperature using microwave and optical techniques. This simple system constitutes a particularly convenient platform for further exploring the dynamics of symmetry breaking.

Spin waves, the collective excitations of the magnetic order parameter, and magnons, the associated quasiparticles, are envisioned as possible data carriers in future wave-based computing architectures. On the road towards spin-wave computing, the development of a diode-like device capable of transmitting spin waves in only one direction, thus allowing controlled signal routing, is an essential step. Here, we report on the design and experimental realization of a microstructured magnonic diode in a ferromagnetic bilayer system. Effective unidirectional propagation of spin waves is achieved by taking advantage of nonreciprocities produced by dynamic dipolar interactions in transversally magnetized media, which lack symmetry about their horizontal midplane. More specifically, dipolar-induced nonreciprocities are used to engineer the spin-wave dispersion relation of the bilayer system so that the group velocity is reduced to very low values for one direction of propagation, and not for the other, thus producing unidirectional slow spin waves. Brillouin light scattering and propagating spin-wave spectroscopy are used to demonstrate the diode-like behavior of the device, the composition of which was previously optimized through micromagnetic simulations. simulations.

We report on propagating spin-wave spectroscopy measurements carried out on coplanar nano-antenna devices made from a Si/SiO\\(_2\\)/Ru(5nm)/Co(20)/Pt(5nm) film. The measurements were analyzed in detail by employing newly developed theoretical modeling and de-embedding procedures. The magnetic parameters of the film were determined by complementary Brillouin light scattering and ferromagnetic resonance measurements. The propagating spin wave signals could be accounted for quantitatively for the range of externally applied magnetic fields investigated in this study: 130-1500 Oe.

We report a detailed study of the ultra slow domain wall motion controlling the magnetization reversal process in ferromagnetic thin films under weak applied fields, in the stationary creep regime, where the domain wall jumps between deep metastable states through thermally nucleated localized displacements. By determining the areas irreversibly reversed in consecutive time windows of different durations, we are able to resolve the non-gaussian statistics of the intermittent domain growth, for domain wall mean velocities as small as \\(v \\approx 1 ~\\text{nm/s}\\). Our observations are quantitatively consistent with the existence of creep avalanches: roughly independent clusters with broad size and ignition-time distributions, each one composed by a large number of spatio-temporally correlated thermally activated elementary events.