## About

189

Publications

25,297

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3,773

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Introduction

Additional affiliations

May 1995 - April 2024

Education

March 1988 - June 1993

**Pontificia Universidad Católica de Chile**

Field of study

- Doctor en Ciencias Exactas con Mención en Física

## Publications

Publications (189)

This work analyzes the nucleation and stabilization of torons in cylindrical nanopillars with bulk DMI and easy-plane anisotropy. A micromagnetic study reveals the dependence of toron chains on the nanopillar length and the different behaviors when nucleating an even or odd number of torons in a magnetic nanopillar. Spin wave resonant modes in thes...

This work analyzes the propagation of a transverse domain wall (DW) under the action of an electric current along a nanowire with a curvature gradient. Our results evidence that the...

Using numerical simulations, we explore the static and dynamic response of hopfions to an external magnetic field in cylindrical and toroidal nanorings. Results evidence that the nucleation and stability of hopfions are intricately linked to geometry. When including an external field, due to the Dzyaloshinskii–Moriya interaction and the field direc...

Cylindrical magnetic nanowires (NWs) constitute a viable component of 3D nanoscale magnetic devices and engineering their response to external stimuli is necessary for their future functionalization. Here, by means of micromagnetic simulations, we study the dynamical response of vortex–antivortex and Bloch point domain walls under the action of an...

An off-center shift of the magnetic hysteresis loop, usually known as exchange bias, develops in an asymmetric nanodisk due to the Dzyaloshinskii-Moriya (DM) interaction. Results exhibit the onset of bias in a system without material interfaces, originating from the relation between the chirality defined by the DM interaction and the geometry. In a...

In this work, we present a theoretical model for domain wall (DW) oscillations in a curved magnetic nanowire with a constant curvature under the action of a uniaxial magnetic field. Our results show that the DW dynamics can be described as that of the mechanical pendulum, and both the NW curvature and the external magnetic field influence its oscil...

Hopfions are localized and topologically nontrivial magnetic configurations that have received considerable attention in recent years. In this Letter, we use a micromagnetic approach to analyze the scattering of spin waves (SWs) by magnetic hopfions. Our results evidence that SWs experience an electromagnetic field generated by the hopfion and shar...

In this paper, we address the skyrmion-bimeron dynamical transformation during the propagation of such structures along a magnetic nanotrack with anisotropy gradients. Using a micromagnetic approach and simulations, we observe that a skyrmion continuously transforms into a bimeron, and vice versa (in a reversible way). Furthermore, our results show...

This work analyzes the propagation of a transverse domain wall (DW) motion under the action of an electric current along a nanowire (NW) with a curvature gradient. Our results evidence that the curvature gradient induces a chiral spin-transfer torque (CSTT) whose effect on the DW motion depends on the direction along which the DW points. The origin...

Citation: Castillo-Sepúlveda, S.; Corona, R.M.; Saavedra, E.; Laroze, D.; Espejo, A.P.; Carvalho-Santos, Abstract: This work analyzes the magnetic configurations of cylindrical nanowires with a bulk Dzyaloshinskii-Moriya interaction and easy-plane anisotropy. We show that this system allows the nucleation of a metastable toron chain even when no ou...

Hopfions are localized and topologically non-trivial magnetic configurations that have received considerable attention in recent years. Through a micromagnetic approach, we analyze the scattering of spin waves by magnetic hopfions. We show that the spin waves experience an emergent electromagnetic field related to the topological properties of the...

Three dimensional magnetic textures are a cornerstone in magnetism researches. In this work, we analyze the stabilization and dynamic response of a magnetic hopfion hosted in a toroidal nanoring with intrinsic Dzialoshinskii-Moriya interaction simulating FeGe. Our results evidence that unlike their planar counterpart, where perpendicular magnetic a...

This paper focuses on the dynamics of a domain wall (DW) displacing along an elliptically bent nanowire (NW) under the action of spin-polarized electric currents and external magnetic fields. Our results evidence that a curvature gradient induces an exchange-driven effective tangential field responsible for pinning a DW at the maximum curvature poi...

Using numerical simulations, we studied the dynamics of two skyrmions nucleated in a double-disk structure. Depending on the geometry and the electric current, different regimes for the dynamical behavior of the skyrmions were obtained. Our results evidence that there are four main dynamic regimes depending on the geometry and current: stagnation p...

The dynamics of several systems in nature occurs under some constraints and symmetries that ensure the appearance of constants of motion. In this work, we discuss the dynamics of the magnetic domain wall (DW) under the Walker regime (i.e., when its position oscillates as a function of time) in bent cylindrical magnetic nanowires (NWs) with constant...

In this work, we present an analysis of skyrmion dynamics considering Dzyaloshinskii–Moriya interactions in an STNO device with a double-disk geometry. Three regimes were observed as a function of geometric parameters and the electric current density: (i) the skyrmion is annihilating at the system’s border; (ii) the skyrmion moves in a non-circular...

Understanding the domain wall (DW) dynamics in magnetic nanowires (NW) is crucial for spintronic-based applications demanding the use of DWs as information carriers. This work focuses on the dynamics of a DW displacing along a bent NW with an elliptical shape under the action of spin-polarized electric currents and external magnetic fields. Our res...

In this work we analyze the influence of curvature on the dynamic properties of the magnetization in bent nanotubes. Our results show that both the resonance frequencies and the number of resonant peaks have a strong dependence on the ground state of the magnetization created by the curvature. Our results can be understood from the analysis of the...

The search for magnetic hopfions has been the focus of intense research during the last years. In this direction, and using micromagnetic simulations, we studied the magnetization reversal mechanism in toroidal nanoparticles under the action of an Oersted magnetic field. Our results evidence the nucleation of four magnetic configurations as a funct...

Understanding and mastering the magnetic properties of domain walls in cylindrical nanowires is a fundamental pillar for developing novel 3D information technologies. For this purpose, a good comprehension of domain walls (DW) dynamical properties, which are strongly dependent on its type and size, is needed. In this work by means of micromagnetic...

When the skyrmion dynamics beyond the particle-like description is considered, this topological structure can deform due to a self-induced field. In this work, we perform Monte Carlo simulations to characterize the skyrmion deformation during its steady movement. In the low-velocity regime, the deformation in the skyrmion shape is quantified by an...

The interplay between curvature and magnetization is a cornerstone in magnetism. Thus, in this work, we address the role of curvature on the propagation of magnetic skyrmions along a curved race track. Using a micromagnetic approach and simulations, we observed the creation of a curvature-induced force (CIF) that acts on the skyrmion while travelin...

We investigate the dynamics of a transverse domain wall (DW) in a bent nanostripe under an external field and spin-polarized current. Besides the standard Walker breakdown phenomenon, we show the emergence of a second Walker-like critical field, which depends on both the curvature of the nanostripe and its cross section geometry. At this field, DW...

The study of patterned magnetic elements that can sustain more than one bit of the information is an important research line for developing new routes in magnetic storage and magnetic logic devices. Previous Monte Carlo studies of T-shaped magnetic nanostructures revealed the equilibrium and evolution of magnetic states that could be found as a res...

Magnetic skyrmions are quasiparticle-like textures that are topologically different from a single domain magnetization state. Their topological protection, combined with the low current density needed to move them, make these objects relevant to be used as information storage structures. In such a context, the analysis of the interactions between s...

The understanding of the domain wall (DW) dynamics along magnetic nanowires is crucial for spintronic applications. In this work, we perform a detailed analysis of the transverse DW motion along nanowires with polygonal cross-sections. If the DW displaces under a magnetic field above the Walker limit, the oscillatory motion of the DW is observed. T...

In this work we performed a detailed numerical analysis on the static and dynamic properties of magnetic antidot arrays as a function of their geometry. In particular, we explored how by varying the shape of these antidot arrays from circular holes to stadium-shaped holes, we can effectively control the magnetic properties of the array. Using micro...

Vortex domain walls (DWs) are characterized by their chirality, an important property that needs to be controlled for the use of such walls in potential technological applications. In this work we explore a wire-ring structure in which we have alternate hard and soft magnetic materials. Our results evidence that, depending on the materials, it is p...

In this work, the current-induced inertial effects on skyrmions hosted in ferromagnetic systems are studied. {When the dynamics is considered beyond the particle-like description, magnetic skyrmions can deform due to a self-induced field. We perform Monte Carlo simulations to characterize the deformation of the skyrmion during its movement}. In the...

During the last years, topologically protected collective modes of magnetization have called much attention. Among these, skyrmions and merons have been objects of intense study. In particular, topological skyrmions are structures with an integer skyrmion number Q while merons have a half-integer skyrmion charge q. In this paper, we consider a Q=1...

The study of curvature-induced effects on the properties of nanostructures has become a cornerstone of magnetism. However, several methodologies usually used for studying nanoscale magnetic systems present difficulties for adequately describing curvature. In this work, we present a method that allows studying, under specific conditions, curved dome...

The control of magnetic interactions is one of the most relevant topics in spintronics. In this work, we propose to use electric potential barriers for tuning or even suppressing the RKKY exchange coupling between magnetic impurities in a two-dimensional electron gas. Our results show that it is possible to manipulate both the magnitude and sign of...

Magnetic cylindrical nanowires are promising candidates for future three-dimensional nanotechnology. Domain walls (DWs) in magnetic nanowires play the role of information carriers, and the development of applications requires proper description of their dynamics. Here we perform a detailed analytical and numerical analysis of the DW motion along a...

Magnetic nanotubes have been widely studied because they are promising candidates to be part of devices based on spintronic and magnonic technologies. However, the experimental techniques used to prepare such structures cannot guarantee the generation of perfect elements, and some geometric imperfections can appear. In this direction, the existence...

In this paper, by means of analytical calculations and a simple model, we studied the effect of curvature in magnetic thin stripes. Three different domain walls were observed, depending on the slab geometry. A phase diagram that shows the geometric parameters at which each domain wall is preferred was obtained. The presented methodology can also be...

Skyrmions have become one of the most visited topics during the last decade in condensed matter physics. In this work, and by means of analytical calculations and micromagnetic simulations, we explore the effect of the magnetostatic field generated by a magnetic tip on the stability of skyrmions. Our results show that the interaction energy between...

In the last years, electric fields have been used to control the magnetic exchange interactions and anisotropies in nanometric devices. In this paper, we study the spin-spin exchange interaction between two magnetic impurities embedded in a three-dimensional nonrelativistic electron gas, namely the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction....

Curvature of nanomagnets can be used to induce chiral textures in the magnetization field. Here we perform analytical calculations and micromagnetic simulations aiming to analyze the stability of in-surface magnetization configurations in toroidal nanomagnets. We have obtained that despite toroidal vortex-like configurations are highly stable in ma...

Skyrmions have become one of the most visited topics during the last decade in condensed matter physics. In this work, and by means of analytical calculations and micromagnetic simulations, we explore the effect of the magnetostatic field generated by a magnetic tip on the stability of skyrmions. Our results show that the interaction energy between...

The magnetization dynamics of nano-oscillators may be excited by both magnetic fields and spin-polarized currents. While the dynamics of single oscillators has been well characterized, the synchronization of several ones is not fully understood yet. An analytical and numerical study of the nonlinear dynamics of two magnetostatically coupled spin va...

The magnetic energy of nanorings with variable anisotropy along their radius have been studied using analytical calculations and micromagnetic simulations. Based on the geometric characteristics of nanorings, four magnetic states are considered, looking to the relatively lower energy magnetization configuration as a function of anisotropy and geome...

During the last years, there has been a growing interest in the coupling between voltages and the magnetization of insulating nanostructures. Applied voltages can change the magnetic anisotropy of magnetic tunnel junctions and generate magnetization dynamics more efficiently than alternating magnetic fields and spin-polarized electric currents beca...

Curvature of nanomagnets can be used to induce chiral textures in the magnetization field. Here we perform analytical calculations and micromagnetic simulations aiming to analyze the stability of in-surface magnetization configurations in toroidal nanomagnets. We have obtained that despite toroidal vortex-like configurations are highly stable in ma...

A discussion on the interaction between skyrmions in a bi-layer system connected by a non-magnetic metal is presented. Using a free charge carrier model, we have shown that, depending on the spacer thickness, the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction can induce attractive or repulsive interactions. We have also shown that due to an incre...

Magnetic nanorings have been widely studied due to their potential applications in spintronic and magnonic devices. In this work, by means of analytical calculations and micromagnetic simulations we have analyzed the magnetic energy of nanorings with variable anisotropy along their radius. Four magnetic states, including two new magnetic configurat...

A detailed analytical and numerical study of the spin wave modes of two nanopillar spin torque nano-oscillators coupled by magnetostatic interactions is presented under the macrospin approximation. Results show that the normal modes of the system oscillate with the magnetizations in-phase or anti-phase in both disks. The frequencies and critical cu...

A discussion on the interaction between skyrmions in a bi-layer system connected by a non-magnetic metal is presented. From considering a free charge carrier model, we have shown that the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction can induce attractive or repulsive interaction between the skyrmions depending on the spacer thickness. We have a...

A discussion on the interaction between skyrmions in a bi-layer system connected by a non-magnetic metal is presented. From considering a free charge carrier model, we have shown that the Ruderman-Kittel-Kasuya-Yosida (RKKY ) inter- action can induce attractive or repulsive interaction between the skyrmions depending on the spacer thickness. We hav...

By means of Monte Carlo simulations we studied field driven nucleation and propagation of transverse domain walls (DWs) in magnetic nanowires subjected to temperature gradients. Simulations identified the existence of critical thermal gradients that allow the existence of reversal processes driven by a single DW. Critical thermal gradients depend o...

A detailed analytical and numerical study of the spin wave modes of the free layer of a nanopillar spin torque nano-oscillator (STNO) has been performed as a function of the magnetostatic interaction between the free and the fixed magnetic layers. Results for higher frequency normal modes show that the magnetostatic interaction does not appreciably...

Understanding the domain wall dynamics is an important issue in modern magnetism. Here we present results of domain wall displacement in curved cylindrical nanowires at a constant magnetic field. We show that the average velocity of a transverse domain wall increases with curvature. Contrary to what it is observed in stripes, in a curved wire the t...

The recently introduced area of topological magnetism searches for equilibrium structures stabilized by a combination of interactions and specific boundary conditions. Until now, the internal energy of open magnetic chains has been explored. Here, we study the energy landscape of closed magnetic chains with on-site anisotropy coupled with antiferro...

The magnetization reversal mechanisms in soft/hard multisegmented nanowires have been inves- tigated using numerical simulations. In most of the studied systems the magnetization reversal process starts at the ends. However in short soft/hard/soft nanowires, the magnetization reversal process starts at the center of the wire, generating an unusual...

The magnetic stability of a multilayer system formed by N slabs separated by non-magnetic spacers has been studied emphasizing the role of dipolar interactions among magnetic slabs. By means of numerical and analytical calculations we have identified a regime at which the magnetic slabs behave as independent, i.e., a critical thickness of the space...

Based on Monte Carlo numerical simulations results for the magnetization reversal process in thin circular Ni dots connected by a bridge are presented. The dependence of the process on both the width of the bridge and the orientation of the applied magnetic field has been investigated. It was found that when the applied magnetic field is set parall...

Segmented magnetic nanowires are a promising route for the development of three dimensional data storage techniques. Such devices require a control of the coercive field and the coupling mechanisms between individual magnetic elements. In our study, we investigate electrodeposited nanomagnets within host templates using vibrating sample magnetometr...

In this work, we study nonlinear aspects of the deterministic spin dynamics of an anisotropic single-domain magnetic particle at finite temperature modeled by the Landau-Lifshitz-Bloch equation. The magnetic field has two components: a constant term and a term involving a harmonic time modulation. The dynamical behavior of the system is characteriz...

Field driven nucleation and propagation of transverse domain walls (DWs) in Fe nanowires under thermal gradients were studied using Monte Carlo simulations. Simulations identified that thermal gradients contribute to stabilizing nucleation of multiple DWs. The results also showed that the correct combination of a magnetic field and temperature grad...

Mosaic nanocomposites composed of nickel and cobalt nanowires arranged in different configurations were investigated using Monte Carlo simulations and a simple model that considers single-domain structures including length corrections due to the shape anisotropy. Our results showed that for an ordered array both the coercivity and the remanence dec...

In this work, and by means of micromagnetic simulations, we study the magnetic properties of toroidal nanomagnets. The magnetization ground state for different values of the aspect ratio between the toroidal and polar radii of the nanotorus has been obtained. The hysteresis curves are also obtained, evidencing the existence of two reversal modes de...

The magnetic properties of a thin film consisting of an exchange-coupled [Co/Ni][subscript 2]/NiFe multilayer have been studied as a function of the NiFe thickness by using Monte Carlo modeling and compared with experimental results of [Co/Ni][subscript 4]/Co/NiFe multilayers. Both modeling and experiment showed that the NiFe thickness controls the...

The relative stability of out-of-plane ferromagnetic, vortex without core and vortex with core configurations in cylindrical nanostructures are examined in terms of their geometric and magnetic parameters. Numerical simulations are done for general geometrical structures, while analytical expressions are obtained in the limiting cases of very long...

In response to ultrafast laser pulses, single-phase metals have been classified as "fast" (with magnetization quenching on the time scale of the order of 100 fs and recovery in the time scale of several picoseconds and below) and "slow" (with longer characteristic time scales). Disordered ferrimagnetic alloys consisting of a combination of "fast" t...

The simulated annealing algorithm, a method commonly used to calculate properties of condensed-matter systems, is used to calculate entanglement of formation for higher-dimensional mixed states. The method relies on representing a mixed state as a pure state in an enlarged Hilbert space, and on the search for the extension minimizing the convex roo...

The occurrence of equilibrium magnetic configurations in ferromagnetic low-symmetry nanoparticles has been investigated. T-shaped nanoparticles, which present strong configurational anisotropy, have been considered. It has been found that such particles exhibit four equilibrium magnetic states, whose stability at room temperature was estimated. The...

Using a simple method we produce polyethylene film with embedded chains of cobalt nanoparticles. The crystalline magnetic nanoparticles were synthesized through a simple chemical reduction method at room temperature using ultrasonic assistance. These particles were incorporated in a polyethylene matrix using a solution blending mechanism under an e...