Danila Amoroso
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Research Subjects
Danila Amoroso has a total of 37 co-authors. Here are the top co-authors by number of shared publications:
Silvia Picozzi
Consiglio Nazionale delle Ricerche CNR-SPIN, c/o Universitá degli Studi'G. D'Annunzio', 66100, Chieti, Italy
5 shared publications- Paolo Barone
CNR-SPIN Institute for Superconducting and other Innovative Materials and Devices, Area della Ricerca di Tor Vergata, Via del Fosso del Cavaliere 100, I-00133 Rome, Italy
4 shared publications - Kunihiko Yamauchi
The University of Osaka
2 shared publications - Thi Phuong Thao Nguyen
Department of Precision Engineering, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
2 shared publications Aleksandar Razpopov
Institut für Theoretische Physik, Goethe-Universität Frankfurt, Max-von-Laue-Straße 1, 60438 Frankfurt am Main, Germany
1 shared publication- Alexander Edström
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Spain
1 shared publication
Latest Publications
- 3 April 2026
- Published by Agence Bibliographique de l'Enseignement Supérieur
First-principles study of piezoelectric (Ba,Ca)TiO3-Ba(Ti,Zr)O3 solid solutions
Étude ab-initio de solutions solides piézoélectriques (Ba,Ca)TiO3-Ba(Ti,Zr)O3: Les piézoélectriques à haute performance sont des composants clés pour les dispositifs agiles. Il a été démontré récemment que les solutions solides (Ba,Ca)(Ti,Zr)O3 (BCTZ) présentent des propriétés électromécaniques prometteuses. Cependant, les mécanismes microscopiques conduisant à de telles caractéristiques restent à éclaircir, et les investigations théoriques de BCTZ demeurent très limitées à ce jour. En conséquence, cette thèse propose d’étudier les propriétés de différentes compositions de solutions solides (Ba,Ca)TiO3-Ba(Ti,Zr)O3 au moyen de calculs de premiers principes, en mettant l’accent sur la dynamiquedu réseau et sur la compétition entre différentes phases ferroélectriques. Nous nous intéressons d’abord aux quatre composés parents BaTiO3, CaTiO3, BaZrO3 et CaZrO3, afin de comparer leurs propriétés et leurs différentes tendances à la ferroélectricité. Ensuite, le coeur de notre étude est une caractérisation systématique des systèmes binaires (Ba,Ca)TiO3 et Ba(Ti,Zr)O3 en utilisant à la fois l’approximation du cristal virtuel (VCA) et des calculs directs sur supercellules.Lorsqu’on passe continument de BaTiO3 à CaTiO3 dans (Ba,Ca)TiO3, la caractéristique principale est une transformation progressive de la ferroélectricité de type B en type A en raison d’effets stériques, lesquels déterminent en grande partie le comportement du système. En particulier, pour les petites concentrations en calcium, nous avons mis en évidence que laferroélectricité guidée par le site B est globalement affaiblie, conduisant à la disparition de la barrière d’énergie entre différents états polaires et à une polarisation quasi-isotrope. Une amélioration considérable de la réponse piézoélectrique résulte de ces caractéristiques. En passant de BaTiO3 à BaZrO3 dans Ba(Ti,Zr)O3, en revanche, le comportement est dominé parles mouvements coopératifs Zr-Ti et l’électrostatique locale. En particulier, la phase R3m est stabilisée significativement pour les faibles concentrations en zirconium. Sous l’effet d’une augmentation de la concentration en zirconium, le système montre une tendance à la réduction de la distorsion polaire; néanmoins, la ferroélectricité peut être préservée localement dans les régionsriches en titane. Grâce à un modèle électrostatique basé sur un super-réseau BaZrO3/mBaTiO3, nous avons également découvert une activation polaire inattendue pour Zr, en fonction d’un ordre atomique spécifique. Un facteur microscopique expliquant la réponse piézoélectrique exaltée dans BCTZ, pour de faibles concentrations en Ca et Zr, peut donc résider dans l’interaction entre la ferroélectricité affaiblie induite par Ti et la ferroélectricité émergente induite par Ca, interaction produisant une anisotropie minimale pour la polarisation. En outre, notre étude comparative révèle que la physique microscopique spécifique de ces solutions solides limite sévèrement l’applicabilité de l’approximation du cristal virtuel (VCA) à ces systèmes.
- 3 April 2026
- Published by Agence Bibliographique de l'Enseignement Supérieur
First-principles study of piezoelectric (Ba,Ca)TiO3-Ba(Ti,Zr)O3 solid solutions
Étude ab-initio de solutions solides piézoélectriques (Ba,Ca)TiO3-Ba(Ti,Zr)O3: Les piézoélectriques à haute performance sont des composants clés pour les dispositifs agiles. Il a été démontré récemment que les solutions solides (Ba,Ca)(Ti,Zr)O3 (BCTZ) présentent des propriétés électromécaniques prometteuses. Cependant, les mécanismes microscopiques conduisant à de telles caractéristiques restent à éclaircir, et les investigations théoriques de BCTZ demeurent très limitées à ce jour. En conséquence, cette thèse propose d’étudier les propriétés de différentes compositions de solutions solides (Ba,Ca)TiO3-Ba(Ti,Zr)O3 au moyen de calculs de premiers principes, en mettant l’accent sur la dynamiquedu réseau et sur la compétition entre différentes phases ferroélectriques. Nous nous intéressons d’abord aux quatre composés parents BaTiO3, CaTiO3, BaZrO3 et CaZrO3, afin de comparer leurs propriétés et leurs différentes tendances à la ferroélectricité. Ensuite, le coeur de notre étude est une caractérisation systématique des systèmes binaires (Ba,Ca)TiO3 et Ba(Ti,Zr)O3 en utilisant à la fois l’approximation du cristal virtuel (VCA) et des calculs directs sur supercellules.Lorsqu’on passe continument de BaTiO3 à CaTiO3 dans (Ba,Ca)TiO3, la caractéristique principale est une transformation progressive de la ferroélectricité de type B en type A en raison d’effets stériques, lesquels déterminent en grande partie le comportement du système. En particulier, pour les petites concentrations en calcium, nous avons mis en évidence que laferroélectricité guidée par le site B est globalement affaiblie, conduisant à la disparition de la barrière d’énergie entre différents états polaires et à une polarisation quasi-isotrope. Une amélioration considérable de la réponse piézoélectrique résulte de ces caractéristiques. En passant de BaTiO3 à BaZrO3 dans Ba(Ti,Zr)O3, en revanche, le comportement est dominé parles mouvements coopératifs Zr-Ti et l’électrostatique locale. En particulier, la phase R3m est stabilisée significativement pour les faibles concentrations en zirconium. Sous l’effet d’une augmentation de la concentration en zirconium, le système montre une tendance à la réduction de la distorsion polaire; néanmoins, la ferroélectricité peut être préservée localement dans les régionsriches en titane. Grâce à un modèle électrostatique basé sur un super-réseau BaZrO3/mBaTiO3, nous avons également découvert une activation polaire inattendue pour Zr, en fonction d’un ordre atomique spécifique. Un facteur microscopique expliquant la réponse piézoélectrique exaltée dans BCTZ, pour de faibles concentrations en Ca et Zr, peut donc résider dans l’interaction entre la ferroélectricité affaiblie induite par Ti et la ferroélectricité émergente induite par Ca, interaction produisant une anisotropie minimale pour la polarisation. En outre, notre étude comparative révèle que la physique microscopique spécifique de ces solutions solides limite sévèrement l’applicabilité de l’approximation du cristal virtuel (VCA) à ces systèmes.
- 28 March 2023
- Published by American Physical Society (APS) in Physical Review B
- Vol. 107 (10) , 104427
Unraveling the role of Sm electrons in the magnetism ofMagnetic rare-earth orthoferrites host a variety of functional properties from multiferroicity and strong magnetostriction to spin-reorientation transitions and ultrafast light-driven manipulation of magnetism, which can be exploited in spintronics and next-generation devices. Among these systems, is attracting particular interest for its rich phase diagram and the high temperature Fe-spin magnetic transitions, which combines with a very low temperature and as yet unclear Sm-spin ordering. Various experiments suggest that the interaction between the Sm and Fe magnetic moments (further supported by the magnetic anisotropy), is at the origin of the complex cascade of transitions, but a conclusive and clear picture has not yet been reached. In this paper, by means of comprehensive first-principles calculations, we unravel the role of the magnetic Sm ions in the Fe-spin reorientation transition and in the detected anomalies in the lattice vibrational spectrum, which are a signature of a relevant spin-phonon coupling. By including both Sm- electrons and noncollinear magnetism, we find frustrated and anisotropic Sm interactions, and a large magnetocrystalline anisotropy mediated by the SOC of the Sm- electrons, which drive the complex magnetic properties and phase diagram of .- 28 March 2023
- Published by American Physical Society (APS) in Physical Review B
- Vol. 107 (10) , 104427
Unraveling the role of Sm electrons in the magnetism ofMagnetic rare-earth orthoferrites host a variety of functional properties from multiferroicity and strong magnetostriction to spin-reorientation transitions and ultrafast light-driven manipulation of magnetism, which can be exploited in spintronics and next-generation devices. Among these systems, is attracting particular interest for its rich phase diagram and the high temperature Fe-spin magnetic transitions, which combines with a very low temperature and as yet unclear Sm-spin ordering. Various experiments suggest that the interaction between the Sm and Fe magnetic moments (further supported by the magnetic anisotropy), is at the origin of the complex cascade of transitions, but a conclusive and clear picture has not yet been reached. In this paper, by means of comprehensive first-principles calculations, we unravel the role of the magnetic Sm ions in the Fe-spin reorientation transition and in the detected anomalies in the lattice vibrational spectrum, which are a signature of a relevant spin-phonon coupling. By including both Sm- electrons and noncollinear magnetism, we find frustrated and anisotropic Sm interactions, and a large magnetocrystalline anisotropy mediated by the SOC of the Sm- electrons, which drive the complex magnetic properties and phase diagram of .- 16 August 2022
- Published by American Physical Society (APS) in Physical Review B
- Vol. 106 (6) , 064105
Stability of the tetragonal phase of under high pressureIn this paper, we revisit the high pressure behavior of by a combination of first-principle calculations, Raman spectroscopy and x-ray diffraction under high pressure. We confirm experimentally the cubic-to-tetragonal transition at and find no evidence for any other phase transition up to , the highest pressures investigated, at variance with past reports. We reinvestigate phase stability with density functional theory considering not only the known tetragonal () phase but also other potential antiferrodistortive candidates. This shows that the tetragonal phase becomes progressively more stable upon increasing pressure as compared to phases with more complex tilt systems. The possibility for a second transition to another tilted phase at higher pressures, and in particular to the very common orthorhombic structure, is therefore ruled out.- 16 August 2022
- Published by American Physical Society (APS) in Physical Review B
- Vol. 106 (6) , 064105
Stability of the tetragonal phase of under high pressureIn this paper, we revisit the high pressure behavior of by a combination of first-principle calculations, Raman spectroscopy and x-ray diffraction under high pressure. We confirm experimentally the cubic-to-tetragonal transition at and find no evidence for any other phase transition up to , the highest pressures investigated, at variance with past reports. We reinvestigate phase stability with density functional theory considering not only the known tetragonal () phase but also other potential antiferrodistortive candidates. This shows that the tetragonal phase becomes progressively more stable upon increasing pressure as compared to phases with more complex tilt systems. The possibility for a second transition to another tilted phase at higher pressures, and in particular to the very common orthorhombic structure, is therefore ruled out.- 29 July 2022
- Published by American Physical Society (APS) in Physical Review B
- Vol. 106 (3) , 035156
Microscopic origin of magnetism in monolayer transition metal dihalidesMotivated by the recent wealth of exotic magnetic phases emerging in two-dimensional frustrated lattices, we investigate the origin of possible magnetism in the monolayer family of triangular lattice materials (=V, Mn, Ni and =Cl, Br, I). We first show that consideration of general properties such as filling and hybridization enables to formulate the trends for the most relevant magnetic interaction parameters. In particular, we observe that the effects of spin-orbit coupling (SOC) can be effectively tuned through the ligand elements as the considered transition metal ions do not strongly contribute to the anisotropic component of the intersite exchange interaction. Consequently, we find that the corresponding SOC matrix elements differ significantly from the atomic limit. In the next step and by using two ab initio based complementary approaches, we extract realistic effective spin models and find that in the case of heavy ligand elements, SOC effects manifest in anisotropic exchange and single-ion anisotropy only for specific fillings.- 29 July 2022
- Published by American Physical Society (APS) in Physical Review B
- Vol. 106 (3) , 035156
Microscopic origin of magnetism in monolayer transition metal dihalidesMotivated by the recent wealth of exotic magnetic phases emerging in two-dimensional frustrated lattices, we investigate the origin of possible magnetism in the monolayer family of triangular lattice materials (=V, Mn, Ni and =Cl, Br, I). We first show that consideration of general properties such as filling and hybridization enables to formulate the trends for the most relevant magnetic interaction parameters. In particular, we observe that the effects of spin-orbit coupling (SOC) can be effectively tuned through the ligand elements as the considered transition metal ions do not strongly contribute to the anisotropic component of the intersite exchange interaction. Consequently, we find that the corresponding SOC matrix elements differ significantly from the atomic limit. In the next step and by using two ab initio based complementary approaches, we extract realistic effective spin models and find that in the case of heavy ligand elements, SOC effects manifest in anisotropic exchange and single-ion anisotropy only for specific fillings.- 7 June 2022
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 131 (21) , 215703
Toward machine learning for microscopic mechanisms: A formula search for crystal structure stability based on atomic properties
Machine-learning techniques are revolutionizing the way to perform efficient materials modeling. We here propose a combinatorial machine-learning approach to obtain physical formulas based on simple and easily accessible ingredients, such as atomic properties. The latter are used to build materials features that are finally employed, through linear regression, to predict the energetic stability of semiconducting binary compounds with respect to zinc blende and rocksalt crystal structures. The adopted models are trained using a dataset built from first-principles calculations. Our results show that already one-dimensional (1D) formulas well describe the energetics; a simple grid-search optimization of the automatically obtained 1D-formulas enhances the prediction performance at a very small computational cost. In addition, our approach allows one to highlight the role of the different atomic properties involved in the formulas. The computed formulas clearly indicate that “spatial” atomic properties (i.e., radii indicating maximum probability densities for electronic shells) drive the stabilization of one crystal structure with respect to the other, suggesting the major relevance of the radius associated with the -shell of the cation species.- 7 June 2022
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 131 (21) , 215703
Toward machine learning for microscopic mechanisms: A formula search for crystal structure stability based on atomic properties
Machine-learning techniques are revolutionizing the way to perform efficient materials modeling. We here propose a combinatorial machine-learning approach to obtain physical formulas based on simple and easily accessible ingredients, such as atomic properties. The latter are used to build materials features that are finally employed, through linear regression, to predict the energetic stability of semiconducting binary compounds with respect to zinc blende and rocksalt crystal structures. The adopted models are trained using a dataset built from first-principles calculations. Our results show that already one-dimensional (1D) formulas well describe the energetics; a simple grid-search optimization of the automatically obtained 1D-formulas enhances the prediction performance at a very small computational cost. In addition, our approach allows one to highlight the role of the different atomic properties involved in the formulas. The computed formulas clearly indicate that “spatial” atomic properties (i.e., radii indicating maximum probability densities for electronic shells) drive the stabilization of one crystal structure with respect to the other, suggesting the major relevance of the radius associated with the -shell of the cation species.- Open Access
- 28 April 2022
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 128 (17) , 177202
Curved Magnetism inCurved magnets attract considerable interest for their unusually rich phase diagram, often encompassing exotic (e.g., topological or chiral) spin states. Micromagnetic simulations are playing a central role in the theoretical understanding of such phenomena; their predictive power, however, rests on the availability of reliable model parameters to describe a given material or nanostructure. Here we demonstrate how noncollinear-spin polarized density-functional theory can be used to determine the flexomagnetic coupling coefficients in real systems. By focusing on monolayer , we find a crossover as a function of curvature between a magnetization normal to the surface to a cycloidal state, which we rationalize in terms of effective anisotropy and Dzyaloshinskii-Moriya contributions to the magnetic energy. Our results reveal an unexpectedly large impact of spin-orbit interactions on the curvature-induced anisotropy, which we discuss in the context of existing phenomenological models.- 28 April 2022
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 128 (17) , 177202
Open AccessCurved Magnetism inCurved magnets attract considerable interest for their unusually rich phase diagram, often encompassing exotic (e.g., topological or chiral) spin states. Micromagnetic simulations are playing a central role in the theoretical understanding of such phenomena; their predictive power, however, rests on the availability of reliable model parameters to describe a given material or nanostructure. Here we demonstrate how noncollinear-spin polarized density-functional theory can be used to determine the flexomagnetic coupling coefficients in real systems. By focusing on monolayer , we find a crossover as a function of curvature between a magnetization normal to the surface to a cycloidal state, which we rationalize in terms of effective anisotropy and Dzyaloshinskii-Moriya contributions to the magnetic energy. Our results reveal an unexpectedly large impact of spin-orbit interactions on the curvature-induced anisotropy, which we discuss in the context of existing phenomenological models. - 10 December 2021
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 127 (24) , 247204
Giant Biquadratic Exchange in 2D Magnets and Its Role in Stabilizing Ferromagnetism of MonolayersTwo-dimensional (2D) van der Waals (vdW) magnets provide an ideal platform for exploring, on the fundamental side, new microscopic mechanisms and for developing, on the technological side, ultracompact spintronic applications. So far, bilinear spin Hamiltonians have been commonly adopted to investigate the magnetic properties of 2D magnets, neglecting higher order magnetic interactions. However, we here provide quantitative evidence of giant biquadratic exchange interactions in monolayer (, Br and I), by combining first-principles calculations and the newly developed machine learning method for constructing Hamiltonian. Interestingly, we show that the ferromagnetic ground state within single layers cannot be explained by means of the bilinear Heisenberg Hamiltonian; rather, the nearest-neighbor biquadratic interaction is found to be crucial. Furthermore, using a three-orbitals Hubbard model, we propose that the giant biquadratic exchange interaction originates from large hopping between unoccupied and occupied orbitals on neighboring magnetic ions. On a general framework, our work suggests biquadratic exchange interactions to be important in 2D magnets with edge-shared octahedra.- 10 December 2021
- Published by American Physical Society (APS) in Physical Review Letters
- Vol. 127 (24) , 247204
Giant Biquadratic Exchange in 2D Magnets and Its Role in Stabilizing Ferromagnetism of MonolayersTwo-dimensional (2D) van der Waals (vdW) magnets provide an ideal platform for exploring, on the fundamental side, new microscopic mechanisms and for developing, on the technological side, ultracompact spintronic applications. So far, bilinear spin Hamiltonians have been commonly adopted to investigate the magnetic properties of 2D magnets, neglecting higher order magnetic interactions. However, we here provide quantitative evidence of giant biquadratic exchange interactions in monolayer (, Br and I), by combining first-principles calculations and the newly developed machine learning method for constructing Hamiltonian. Interestingly, we show that the ferromagnetic ground state within single layers cannot be explained by means of the bilinear Heisenberg Hamiltonian; rather, the nearest-neighbor biquadratic interaction is found to be crucial. Furthermore, using a three-orbitals Hubbard model, we propose that the giant biquadratic exchange interaction originates from large hopping between unoccupied and occupied orbitals on neighboring magnetic ions. On a general framework, our work suggests biquadratic exchange interactions to be important in 2D magnets with edge-shared octahedra.- Open Access
- 21 July 2021
- Published by MDPI AG in Nanomaterials
- Vol. 11 (8) , 1873
Interplay between Single-Ion and Two-Ion Anisotropies in Frustrated 2D Semiconductors and Tuning of Magnetic Structures Topology
The effects of competing magnetic interactions in stabilizing different spin configurations are drawing renewed attention in order to unveil emerging topological spin textures and to highlight microscopic mechanisms leading to their stabilization. The possible key role of the two-site exchange anisotropy in selecting specific helicity and vorticity of skyrmionic lattices has only recently been proposed. In this work, we explore the phase diagram of a frustrated localized magnet characterized by a two-dimensional centrosymmetric triangular lattice, focusing on the interplay between the two-ion anisotropy and the single-ion anisotropy. The effects of an external magnetic field applied perpendicularly to the magnetic layer, are also investigated. By means of Monte Carlo simulations, we find an abundance of different spin configurations, going from trivial to high-order Q skyrmionic and meronic lattices. In closer detail, we find that a dominant role is played by the two-ion over the single-ion anisotropy in determining the planar spin texture; the strength and the sign of single ion anisotropy, together with the magnitude of the magnetic field, tune the perpendicular spin components, mostly affecting the polarity (and, in turn, the topology) of the spin texture. Our analysis confirms the crucial role of the anisotropic symmetric exchange in systems with dominant short-range interactions; at the same time, we predict a rich variety of complex magnetic textures, which may arise from a fine tuning of competing anisotropic mechanisms.
- 21 July 2021
- Published by MDPI AG in Nanomaterials
- Vol. 11 (8) , 1873
Open AccessInterplay between Single-Ion and Two-Ion Anisotropies in Frustrated 2D Semiconductors and Tuning of Magnetic Structures Topology
The effects of competing magnetic interactions in stabilizing different spin configurations are drawing renewed attention in order to unveil emerging topological spin textures and to highlight microscopic mechanisms leading to their stabilization. The possible key role of the two-site exchange anisotropy in selecting specific helicity and vorticity of skyrmionic lattices has only recently been proposed. In this work, we explore the phase diagram of a frustrated localized magnet characterized by a two-dimensional centrosymmetric triangular lattice, focusing on the interplay between the two-ion anisotropy and the single-ion anisotropy. The effects of an external magnetic field applied perpendicularly to the magnetic layer, are also investigated. By means of Monte Carlo simulations, we find an abundance of different spin configurations, going from trivial to high-order Q skyrmionic and meronic lattices. In closer detail, we find that a dominant role is played by the two-ion over the single-ion anisotropy in determining the planar spin texture; the strength and the sign of single ion anisotropy, together with the magnitude of the magnetic field, tune the perpendicular spin components, mostly affecting the polarity (and, in turn, the topology) of the spin texture. Our analysis confirms the crucial role of the anisotropic symmetric exchange in systems with dominant short-range interactions; at the same time, we predict a rich variety of complex magnetic textures, which may arise from a fine tuning of competing anisotropic mechanisms.
- 13 July 2021
- Published by American Physical Society (APS) in Physical Review B
- Vol. 104 (1) , 014414
Electric-field tuning of the magnetic properties of bilayer : A first-principles studyThe magnetic properties of the two-dimensional bilayer are the focus of our first-principles analysis, highlighting the role of orbital splitting and carried out in comparison with the prototypical case, where the splitting is negligible. In bilayers, the empty state is found to play a crucial role in both stabilizing the insulating state and in determining the interlayer magnetic interaction. Indeed, an analysis based on maximally localized Wannier functions allows one to evaluate the interlayer exchange interactions in two different stackings (labeled AB and ), to interpret the results in terms of the virtual-hopping mechanism, and to highlight the strongest hopping channels underlying the magnetic interlayer coupling. Upon application of electric fields perpendicular to the slab, we find that the magnetic ground state in the stacking can be switched from antiferromagnetic to ferromagnetic, suggesting the bilayer as an appealing candidate for electric-field-driven miniaturized spintronic devices.- 13 July 2021
- Published by American Physical Society (APS) in Physical Review B
- Vol. 104 (1) , 014414
Electric-field tuning of the magnetic properties of bilayer : A first-principles studyThe magnetic properties of the two-dimensional bilayer are the focus of our first-principles analysis, highlighting the role of orbital splitting and carried out in comparison with the prototypical case, where the splitting is negligible. In bilayers, the empty state is found to play a crucial role in both stabilizing the insulating state and in determining the interlayer magnetic interaction. Indeed, an analysis based on maximally localized Wannier functions allows one to evaluate the interlayer exchange interactions in two different stackings (labeled AB and ), to interpret the results in terms of the virtual-hopping mechanism, and to highlight the strongest hopping channels underlying the magnetic interlayer coupling. Upon application of electric fields perpendicular to the slab, we find that the magnetic ground state in the stacking can be switched from antiferromagnetic to ferromagnetic, suggesting the bilayer as an appealing candidate for electric-field-driven miniaturized spintronic devices.- 26 January 2021
- Published by American Physical Society (APS) in Physical Review B
- Vol. 103 (1) , 014116
Microscopic mechanisms behind hyperferroelectricity
Hyperferroelectrics are observing a growing interest thanks to their unique property to retain a spontaneous polarization even in the presence of a depolarizing field, corresponding to zero macroscopic displacement field conditions. Hyperferroelectricity is ascribed to the softening of a polar mode, but the microscopic mechanisms behind this softening are not totally resolved. Here, by means of phonon calculations and force constants analysis, performed in two classes of hyperferroelectrics, the -LiNbO3-type systems and the hexagonal-ABC systems, we unveil the common features in the dynamical properties of a hyperferroelectric that lead the instability: negative or vanishing on-site force constant associated to the cation driving the polar mode and a destabilizing cation-anion interaction; both induced by short-range forces. We also predict a possible enhancement of the hyperferroelectric properties under increasing external positive pressures: pressure strengthens the destabilizing short-range interactions, inducing a stronger mode instability and the increase of the longitudinal mode effective charges associated to the unstable mode. This suggests an eventual enhancement of the polarization under compressive strain.- 26 January 2021
- Published by American Physical Society (APS) in Physical Review B
- Vol. 103 (1) , 014116
Microscopic mechanisms behind hyperferroelectricity
Hyperferroelectrics are observing a growing interest thanks to their unique property to retain a spontaneous polarization even in the presence of a depolarizing field, corresponding to zero macroscopic displacement field conditions. Hyperferroelectricity is ascribed to the softening of a polar mode, but the microscopic mechanisms behind this softening are not totally resolved. Here, by means of phonon calculations and force constants analysis, performed in two classes of hyperferroelectrics, the -LiNbO3-type systems and the hexagonal-ABC systems, we unveil the common features in the dynamical properties of a hyperferroelectric that lead the instability: negative or vanishing on-site force constant associated to the cation driving the polar mode and a destabilizing cation-anion interaction; both induced by short-range forces. We also predict a possible enhancement of the hyperferroelectric properties under increasing external positive pressures: pressure strengthens the destabilizing short-range interactions, inducing a stronger mode instability and the increase of the longitudinal mode effective charges associated to the unstable mode. This suggests an eventual enhancement of the polarization under compressive strain.