arXiv subjects

José J. Baldoví

Publications and source records attributed to José J. Baldoví.

At least 37 records · Page 2Linked to original sources

arXiv2025

Tunable Itinerant Ferromagnetism in the Two-Dimensional FePd$_2$Te$_2$ Hosting 1D Spin Chains

One-dimensional (1D) magnetism offers unidirectional spin interactions that allow unique tunable properties and unconventional spin phenomena. However, it often suffers from poor stability, limiting practical applications. In this regard, integrating 1D magnetism into two-dimensional (2D) materials enables a promising route to stabilize these systems while preserving their anisotropic magnetic characteristics. Here, we focus on the 2D ferromagnet FePd$_2$Te$_2$ (T$_C$ = 183K), which hosts 1D spin chains and strong in-plane anisotropy. Our first-principles calculations reveal highly anisotropic magnetic exchange interactions, confirming its 1D ferromagnetic nature. We modulate this behavior by Co and Ni substitution and introduce two new members of this family, CoPd$_2$Te$_2$ -- a ferromagnet -- and NiPd$_2$Te$_2$. Our results unveil the microscopic mechanisms governing the behaviour of FePd$_2$Te$_2$ and CoPd$_2$Te$_2$. Furthermore, we also demonstrate that the variation of the chain length is key to modulate magnetism. Finally, we determine the magnon dispersion, showcasing a pronounced anisotropy that enables unidirectional magnon propagation.

cond-mat.mtrl-sci↗

arXiv2025

Coupling molecular spin qubits with 2D magnets for coherent magnon manipulation

Magnonics is an emerging field widely considered as a paradigm shift in information technology that uses spin waves for data storage, processing and transmission. However, the coherent control of spin waves in 2D magnets still remains a challenge. Herein, we investigate the interplay between molecular spins and magnons in hybrid heterostructures formed by [CpTi(cot)] and VOPc spin qubits deposited on the surface of the air-stable 2D van der Waals ferromagnet CrSBr using first principles. Our results show that different molecular rotation configurations significantly impact on qubit relaxation time and alter the magnon spectra of the underlying 2D magnet, allowing the chemical coherent control of spin waves in this material. We predict the feasibility of an ultrafast magnon-qubit interface with minimized decoherence, where exchange coupling plays a crucial role. This work opens new avenues for hybrid quantum magnonics, enabling selective tailoring through a versatile chemical approach.

cond-mat.mes-hall↗

arXiv2024

Switchable magnetic phases in CrSBr$_{1-x}$Cl$_x$ and CrSBr/CrSCl heterostructures

Strategies such as chemical substitution, strain engineering and van der Waals stacking offer powerful means to control magnetism in 2D materials, enabling the emergence of novel quantum phenomena. Here, we investigate the magnetic properties of bulk CrSBr$_{1-x}$Cl$_x$ ($x = 0{-}1$) and the strain-dependent switchable magnetic phases in bilayers CrSBr, CrSCl, and CrSBr/CrSCl heterostructures, using firstprinciples calculations. Our findings demonstrate that Cl incorporation in CrSBr induces competing interlayer antiferromagnetic and ferromagnetic couplings, leading to a spin-glass state when the Cl content exceeds a 67%. This is accompanied by a decrease of magnetic anisotropy, where a $XY$-type magnetic ground state is observed in pristine CrSCl. For CrSBr and CrSCl bilayers, we report a reversible strain-induced switching between interlayer antiferromagnetic and ferromagnetic configurations. Furthermore, we reveal the emergence of interfacial ferromagnetism in CrSBr/CrSCl heterostructures, stabilizing an in-plane magnetization axis for CrSCl by proximity to CrSBr. These results underscore the potential of manipulating magnetism in 2D magnetic materials through precise control of magnetic phases.

cond-mat.mtrl-sci↗

arXiv2024

Tailoring the properties of the 2D ferromagnet CrSBr by lanthanide doping

The growing interest in 2D van der Waals (vdW) magnetic materials stems from their unique properties and potential applications in spintronics, magnonics and quantum information technologies. Among them, CrSBr is a semiconductor that stands out, owing to its high Curie temperature (TC ~ 146 K), air stability and tunable electronic and magnetic properties. Here, we present a systematic investigation of the effects of Dy doping (12.5%, 25%, and 50%) on the structural, electronic and magnetic properties of CrSBr monolayer. Our results reveal that Dy incorporation enhances magnetic anisotropy, modulates TC, and can create quasi-1D ferromagnetic chains that arise from competing ferromagnetic and antiferromagnetic interactions. Additionally, we investigate the properties of DySBr, DySI and DySeI monolayers, which are isostructural to the CrSBr. Our results reveal the feasibility of exfoliating them down to the single-layer and the presence of long-range magnetic order at low temperatures, relying on the combination of both weak exchange interactions and large spin-orbit coupling. This work provides insights into tuning the properties of CrSBr through rare earth doping, unlocking new possibilities for advanced applications at the 2D limit.

cond-mat.mtrl-sci↗

arXiv2024

Magnetic proximity effect in biphenylene monolayer from first-principles

On-surface chemistry has emerged as a key technique for designing novel low-dimensional materials, enabling precise manipulation of their electronic and magnetic properties at the atomic scale. It also proves highly effective for the fabrication of heterostructures. Leveraging these benefits, herein, we perform a first principles study of the magnetic proximity effect (MPE) in a heterostructure formed by a monolayer of the two-dimensional carbon allotrope biphenylene network (BPN) deposited on the surface of the above-room-temperature ferrimagnet yttrium iron garnet (YIG). Our results reveal strong hybridization between BPN orbitals and YIG surface states, resulting in non-homogeneous electron transfer and robust MPE. The proposed methodology accurately describes YIG magnetic interactions, allowing us to study the tuning effects of BPN on the magnetic properties of the substrate for the first time. Additionally, we explore the impact of van der Waals (vdW) distance at the interface, finding enhanced spin splitting up to 30% under external pressure. These findings highlight a promising strategy for inducing spin polarization in BPN without chemical modifications, opening new possibilities for BPN-based spintronic devices through the creation of heterostructures with magnetic materials.

cond-mat.mes-hall↗

arXiv2024

Graphendofullerene: a novel molecular two-dimensional ferromagnet

Carbon chemistry has attracted a lot of attention by chemists, physicists and material scientists in the last decades. The recent discovery of graphullerene provides a promising platform for many applications due to its exceptional electronic properties and the possibility to host molecules or clusters inside the fullerene units. Herein, we introduce graphendofullerene, a novel molecular-based two-dimensional (2D) magnetic material formed by trimetallic nitrides clusters encapsulated on graphullerene. Through first-principles calculations, we demonstrate the successful incorporation of the molecules into the 2D network formed by C$_{80}$ fullerenes, which leads to a robust long-range ferromagnetic order with a Curie temperature (Tc) of 38 K. Additionally, we achieve a 45% increase in Tc by strain engineering. These findings open the way for a new family of molecular 2D magnets based on graphendofullerene for advanced technologies.

cond-mat.mtrl-sci↗

arXiv2024

Electrical control of magnons in multiferroic NiI$_2$

Layered van der Waals two-dimensional (2D) magnets are a cornerstone of ultrathin spintronic and magnonic devices. The recent discovery of a 2D multiferroic with strong magnetoelectric coupling in NiI$_2$ offers a promising platform for the electrical control of spin-wave transport. In this work, using ab initio calculations, we investigate how the magnonic properties of monolayer NiI$_2$ can be controlled using an external electric field. We show that the emergence of a ferroelectric polarization leads to an energy splitting in the magnon spectrum, thus establishing a way to detect the electric polarization experimentally. We also show the modulation of the magnon splitting and the energy position of the singularities in magnon DOS by an electric field due to the strong magnetoelectric coupling. Our results highlight the interplay between ferroelectricity and magnons in van der Waals multiferroics and pave the way to design electrically tunable magnetic devices at the 2D limit.

cond-mat.mtrl-sci↗

arXiv2024

Magnon sensing of NO, NO$_2$ and NH$_3$ gas capture on CrSBr monolayer

Air pollution and greenhouse emissions are a significant problem across various sectors, urging the need for advanced technologies to detect and capture harmful gases. In recent years, two-dimensional (2D) materials have attracted an increasing attention due to their large surface-to-volume ratio and reactivity. Herein, we investigate the potential of single-layer CrSBr for gas sensing and capturing by means of first-principles calculations. We explore the adsorption behaviour of different pollutant gases (H$_2$S, NH$_3$, NO, NO$_2$, CO and CO$_2$) on this 2D ferromagnet and the impact of intrinsic defects on its magnetic properties. Interestingly, we find that Br vacancies enhance the adsorption of NH$_3$, NO and NO$_2$ and induces a selective frequency shift on the magnon dispersion. This work motivates the creation of novel magnonic gas sensing devices based on 2D van der Waals magnetic materials.

cond-mat.mtrl-sci↗

arXiv2024

On the origin of the above-room-temperature magnetism in the 2D van der Waals ferromagnet Fe$_3$GaTe$_2$

Recent advancements in 2D magnetic materials have attracted a growing interest driven by their unique properties and potential applications in spintronic devices. However, the scarcity of systems that exhibit magnetism at room-temperature has limited their practical implementation into functional devices. In this work we focus on the recently synthetised van der Waals (vdW) ferromagnet Fe$_3$GaTe$_2$, which exhibits above-room-temperature magnetism (T$_{\mathrm{c}}$ = 350-380 K) and strong perpendicular magnetic anisotropy. Through first-principles calculations, we examine the magnetic properties of Fe$_3$GaTe$_2$ and compare them with the widely known Fe$_3$GeTe$_2$ ferromagnet. Our calculations unveil the complex microscopic mechanisms governing their magnetic behaviour, emphasizing the pivotal role of the ferromagnetic in-plane exchange interactions in the stabilization of the elevated T$_{\mathrm{c}}$ in Fe$_3$GaTe$_2$. Additionally, we predict the stability, strong perpendicular anisotropy and high T$_{\mathrm{c}}$ of single-layer Fe$_3$GaTe$_2$. We also demonstrate the potential of strain engineering and electrostatic doping to modulate its magnetic exchange interactions and anisotropy. Our results incentivise the isolation of the monolayer and pave the way for the future optimization of Fe$_3$GaTe$_2$ in magnetic and spintronic nanodevices.

cond-mat.mtrl-sci↗

arXiv2024

Tracing d-d transitions in FePS$_{3}$ on ultrafast time scales

Excitations between localized 3d states of transition metal ions within crystalline solids, commonly known as d-d transitions, play a pivotal role in diverse phenomena across solid state physics, materials science, and chemistry. These transitions contribute to the coloration in transition metal oxides, catalytic processes on oxide surfaces, and high-temperature superconductivity. They also couple optical excitation to quantized collective phenomena such as phonons and magnons in magnetic systems. Until now, an experimental method to unravel the complex quasiparticle dynamics associated with d-d transitions has remained elusive. We bridge this gap by demonstrating that d-d transitions can be distinctly traced in momentum space and time using time- and angle-resolved photoelectron spectroscopy (trARPES). Through this approach, we can assign specific momentum-dependent characteristics and elucidate the decay mechanisms of specific d-d transitions in FePS$_{3}$, a two-dimensional van der Waals antiferromagnet with a rich array of quantum phenomena stemming from d-d transitions. This study pioneers the use of ARPES in probing the dynamics of d-d transitions across a wide spectrum of solid-state systems.

cond-mat.mtrl-sci↗

arXiv2023

Strain engineering of topological magnons in chromium trihalides from first-principles

Recent experiments evidence the direct observation of spin waves in chromium trihalides and a gap at the Dirac points of the magnon dispersion in bulk CrI$_3$. However, the topological origin of this feature remains unclear and its emergence at the 2D limit has not yet been proven experimentally. Herein, we perform a fully self-consistent ab initio analysis that supports the presence of topological magnons in chromium trihalides monolayers. Our results confirm the existence of a gap around the K high-symmetry point in the linear magnon dispersion of CrI$_3$, which originates as a direct consequence of intralayer Dzyaloshinskii-Moriya (DM) interaction. In addition, our orbital resolved analysis reveals the microscopic mechanisms that can be exploited using strain engineering to increase the strength of the DM interaction and thus control the gap size in CrI$_3$. This paves the way to the further development of this family of materials as building-blocks for topological magnonics at the limit of miniaturization.

cond-mat.mtrl-sci↗

arXiv2022

Tailoring spin waves in 2D transition metal phosphorus trichalcogenides via atomic-layer substitution

The family of two-dimensional (2D) van der Waals transition metal phosphorus trichalcogenides has received a renewed interest due to their intrinsic 2D antiferromagnetism, which proves them as unprecedented and highly tunable building blocks for spintronics and magnonics at the single-layer limit. Herein, motivated by the exciting potential of atomic-substitution demonstrated in Janus transition metal dichalcogenides, we investigate the crystal, electronic and magnetic structure of selenized Janus monolayers based on MnPS$_3$ and NiPS$_3$ from first-principles. In addition, we calculate the magnon dispersion and perform real-time real-space atomistic dynamic simulations to explore the propagation of spin waves in MnPS$_3$, NiPS$_3$, MnPS$_{1.5}$Se$_{1.5}$ and NiPS$_{1.5}$Se$_{1.5}$. Our calculations predict a drastic enhancement of magnetic anisotropy and the emergence of large Dzyaloshinskii-Moriya interactions, which arises from the induced broken inversion symmetry in the 2D Janus layers. These results pave the way to the development of Janus 2D transition metal phosphorus trichalcogenides and highlight their potential for magnonic applications.

cond-mat.mtrl-sci↗

arXiv2022

Probing the spin dimensionality in single-layer CrSBr van der Waals heterostructures by magneto-transport measurements

Two-dimensional (2D) magnetic materials offer unprecedented opportunities for fundamental physics and applied research in spintronics and magnonics. Beyond the pioneering studies on 2D CrI3 and Cr2Ge2Te6, this emerging field has expanded to 2D antiferromagnets exhibiting different spin anisotropies and textures. Of particular interest is the layered metamagnet CrSBr, a relatively air-stable semiconductor formed by antiferromagnetically-coupled ferromagnetic layers (Tc~150 K) that can be exfoliated down to the single-layer. It presents a complex magnetic behavior with a dynamic magnetic crossover leading to a low-temperature hidden order below T*~40 K. Here, we inspect the magneto-transport properties of CrSBr vertical heterostructures in the 2D limit. Our results demonstrate the marked low-dimensional character of the ferromagnetic monolayer, with short-range correlations above Tc and an Ising-type in-plane anisotropy, being the spins spontaneously aligned along the easy-axis b below Tc. By applying moderate magnetic fields along a and c axes, a spin reorientation occurs, leading to a magnetoresistance enhancement below T*. In multilayers, a spin-valve behavior is observed, with negative magnetoresistance strongly enhanced along the three directions below T*. These results show that CrSBr monolayer/bilayer provides an ideal platform for studying and controlling field-induced phenomena in two-dimensions, offering new insights regarding 2D magnets and their integration into vertical spintronic devices.

cond-mat.str-el↗

arXiv2022

Data mining, dashboard and statistical analysis: a powerful framework for the chemical design of molecular nanomagnets

Three decades of research in molecular nanomagnets have raised their magnetic memories from liquid helium to liquid nitrogen temperature thanks to a wise choice of the magnetic ion and coordination environment. Still, serendipity and chemical intuition played a main role. In order to establish a powerful framework for statistically driven chemical design, we collected chemical and physical data for lanthanide-based nanomagnets, catalogued over 1400 published experiments, developed an interactive dashboard (SIMDAVIS) to visualise the dataset, and applied inferential statistical analysis. Our analysis showed that the Arrhenius energy barrier correlates unexpectedly well with the magnetic memory, as both Orbach and Raman processes can be controlled by vibronic coupling. Indeed, only bis-phthalocyaninato sandwiches and metallocenes, with rigid ligands, consistently present magnetic memory up to high temperature. Analysing magnetostructural correlations, we offer promising strategies for improvement, in particular for the preparation of pentagonal bipyramids, where even "softer" complexes are protected against molecular vibrations.

cond-mat.mes-hall↗

arXiv2022

Magnon straintronics in the 2D van der Waals ferromagnet CrSBr from first-principles

The recent isolation of two-dimensional (2D) magnets offers tantalizing opportunities for spintronics and magnonics at the limit of miniaturization. One of the key advantages of atomically-thin materials is their outstanding deformation capacity, which provides an exciting avenue to control their properties by strain engineering. Herein, we investigate the magnetic properties, magnon dispersion and spin dynamics of the air-stable 2D magnetic semiconductor CrSBr ($T_C$ = 146 K) under mechanical strain using first-principles calculations. Our results provide a deep microscopic analysis of the competing interactions that stabilize the long-range ferromagnetic order in the monolayer. We showcase that the magnon dynamics of CrSBr can be modified selectively along the two main crystallographic directions as a function of applied strain, probing the potential of this quasi-1D electronic system for magnon straintronics applications. Moreover, we predict a strain-driven enhancement of $T_C$ considering environmental screening by ~30%, allowing the propagation of spin waves at higher temperatures.

cond-mat.mtrl-sci↗

arXiv2022

Superconducting density of states and bandstructure at the surface of the candidate topological superconductor Au2Pb

The electronic bandstructure of Au$_2$Pb has a Dirac cone which gaps when undergoing a structural transition into a low temperature superconducting phase. This suggests that the superconducting phase ($T_c=1.1$ K) might hold topological properties at the surface. Here we make Scanning Tunneling Microscopy experiments on the surface of superconducting Au$_2$Pb. We measure the superconducting gap and find a sizeable superconducting density of states at the Fermi level. We discuss possible origins for this finding in terms of superconductivity induced into surface states.

cond-mat.supr-con↗

arXiv2021

Quantum coherent spin-electric control in a molecular nanomagnet at clock transitions

Electrical control of spins at the nanoscale offers significant architectural advantages in spintronics, because electric fields can be confined over shorter length scales than magnetic fields. Thus, recent demonstrations of electric-field (E-field) sensitivities in molecular spin materials are tantalising, raising the viability of the quantum analogues of macroscopic magneto-electric devices.However, the E-field sensitivities reported so far are rather weak, prompting the question of how to design molecules with stronger spin-electric couplings. Here we show that one path is to identify an energy scale in the spin spectrum that is associated with a structural degree of freedom with a significant electrical polarisability. We study an example of a molecular nanomagnet in which a small structural distortion establishes clock transitions (i.e. transitions whose energy is to first order independent of magnetic field) in the spin spectrum; the fact that this distortion is associated with an electric dipole allows us to control the clock transition energy to an unprecedented degree. We demonstrate coherent electrical control of the quantum spin state and exploit it to manipulate independently the two magnetically-identical but inversion-related molecules in the unit cell of the crystal. Our findings pave the way for the use of molecular spins in quantum technologies and spintronics.

cond-mat.mes-hall↗

arXiv2021

Insights on the coupling between vibronically active molecular vibrations and lattice phonons in molecular nanomagnets

Spin-lattice relaxation is a key open problem to understand the spin dynamics of single-molecule magnets and molecular spin qubits. While modelling the coupling between spin states and local vibrations allows to determine the more relevant molecular vibrations for spin relaxation, this is not sufficient to explain how energy is dissipated towards the thermal bath. Herein, we employ a simple and efficient model to examine the coupling of local vibrational modes with long-wavelength longitudinal and transverse phonons in the clock-like spin qubit [Ho(W$_5$O$_{18}$)$_2$]$^{9-}$. We find that in crystals of this polyoxometalate the vibrational mode previously found to be vibronically active at low temperature does not couple significantly to lattice phonons. This means that further intramolecular energy transfer via anharmonic vibrations is necessary for spin relaxation in this system. Finally, we discuss implications for the spin-phonon coupling of [Ho(W$_5$O$_{18}$)$_2$]$^{9-}$ deposited on a MgO (001) substrate, offering a simple methodology that can be extrapolated to estimate the effects on spin relaxation of different surfaces, including 2D materials.

physics.atm-clus↗