2023
Carvalho, Pamela C.; Miranda, Ivan P.; Brandão, Jeovani; Bergman, Anders; Cezar, Júlio C.; Klautau, Angela B.; Petrilli, Helena M.
Correlation of Interface Interdiffusion and Skyrmionic Phases Journal Article
Em: Nano Letters, vol. 23, não 11, pp. 4854-4861, 2023, (PMID: 37235539).
@article{doi:10.1021/acs.nanolett.3c00428,
title = {Correlation of Interface Interdiffusion and Skyrmionic Phases},
author = {Pamela C. Carvalho and Ivan P. Miranda and Jeovani Brandão and Anders Bergman and Júlio C. Cezar and Angela B. Klautau and Helena M. Petrilli},
url = {https://doi.org/10.1021/acs.nanolett.3c00428},
doi = {10.1021/acs.nanolett.3c00428},
year = {2023},
date = {2023-01-01},
journal = {Nano Letters},
volume = {23},
number = {11},
pages = {4854-4861},
abstract = {Magnetic skyrmions are prime candidates for the next generation of spintronic devices. Skyrmions and other topological magnetic structures are known to be stabilized by the Dzyaloshinskii-Moriya interaction (DMI) that occurs when the inversion symmetry is broken in thin films. Here, we show by first-principles calculations and atomistic spin dynamics simulations that metastable skyrmionic states can also be found in nominally symmetric multilayered systems. We demonstrate that this is correlated with the large enhancement of the DMI strength due to the presence of local defects. In particular, we find that metastable skyrmions can occur in Pd/Co/Pd multilayers without external magnetic fields and can be stable even near room temperature conditions. Our theoretical findings corroborate with magnetic force microscopy images and X-ray magnetic circular dichroism measurements and highlight the possibility of tuning the intensity of DMI by using interdiffusion at thin film interfaces.},
note = {PMID: 37235539},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Magnetic skyrmions are prime candidates for the next generation of spintronic devices. Skyrmions and other topological magnetic structures are known to be stabilized by the Dzyaloshinskii-Moriya interaction (DMI) that occurs when the inversion symmetry is broken in thin films. Here, we show by first-principles calculations and atomistic spin dynamics simulations that metastable skyrmionic states can also be found in nominally symmetric multilayered systems. We demonstrate that this is correlated with the large enhancement of the DMI strength due to the presence of local defects. In particular, we find that metastable skyrmions can occur in Pd/Co/Pd multilayers without external magnetic fields and can be stable even near room temperature conditions. Our theoretical findings corroborate with magnetic force microscopy images and X-ray magnetic circular dichroism measurements and highlight the possibility of tuning the intensity of DMI by using interdiffusion at thin film interfaces.
Sousa, O. M.; Sorgenfrei, F.; Assali, L. V. C.; Lalic, M. V.; Klautau, Angela B.; Thunström, P.; Araujo, C. M.; Eriksson, O.; Petrilli, H. M.
Pressure effect on the structural, electronic, and magnetic properties of the battery cathode material LiMn2O4: An ab-initio study Journal Article
Em: Journal of Physics and Chemistry of Solids, vol. 175, pp. 111198, 2023, ISSN: 0022-3697.
@article{SOUSA2023111198,
title = {Pressure effect on the structural, electronic, and magnetic properties of the battery cathode material LiMn2O4: An ab-initio study},
author = {O. M. Sousa and F. Sorgenfrei and L. V. C. Assali and M. V. Lalic and Angela B. Klautau and P. Thunström and C. M. Araujo and O. Eriksson and H. M. Petrilli},
url = {https://www.sciencedirect.com/science/article/pii/S0022369722006151},
doi = {https://doi.org/10.1016/j.jpcs.2022.111198},
issn = {0022-3697},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {Journal of Physics and Chemistry of Solids},
volume = {175},
pages = {111198},
abstract = {LiMn2O4 is a battery cathode material with desirable properties such as low cost, low toxicity, high natural abundance of Mn, and environmental compatibility. By means of first-principles calculations, we study the structural, magnetic, and electronic properties of LiMn2O4 under ambient conditions and high hydrostatic pressures (until 20 GPa). We obtain two oxidation states for Mn, even using a cubic structure, which differ in all analyzed properties: structural, electronic, and magnetic. At P > 0, such properties were found to display a standard behavior decreasing smoothly and linearly with pressure. Furthermore, the enthalpy of cubic and orthorhombic structures under low and high-pressure conditions were examined, showing that no cubic to orthorhombic phase transition exists in all the investigated pressure range, nor is a magnetic cubic to a non-magnetic cubic phase transition possible.},
keywords = {Cathode materials, Electronic structure, LiMnO under pressure},
pubstate = {published},
tppubtype = {article}
}
LiMn2O4 is a battery cathode material with desirable properties such as low cost, low toxicity, high natural abundance of Mn, and environmental compatibility. By means of first-principles calculations, we study the structural, magnetic, and electronic properties of LiMn2O4 under ambient conditions and high hydrostatic pressures (until 20 GPa). We obtain two oxidation states for Mn, even using a cubic structure, which differ in all analyzed properties: structural, electronic, and magnetic. At P > 0, such properties were found to display a standard behavior decreasing smoothly and linearly with pressure. Furthermore, the enthalpy of cubic and orthorhombic structures under low and high-pressure conditions were examined, showing that no cubic to orthorhombic phase transition exists in all the investigated pressure range, nor is a magnetic cubic to a non-magnetic cubic phase transition possible.
Cardias, Ramon; Silva, Jhonatan Santos; Bergman, Anders; Szilva, Attila; Kvashnin, Yaroslav O.; Fransson, Jonas; Klautau, Angela B.; Eriksson, Olle; Delin, Anna; Nordström, Lars
Unraveling the connection between high-order magnetic interactions and local-to-global spin Hamiltonian in non-collinear magnetic dimers Working paper
2023.
@workingpaper{cardias2023unraveling,
title = {Unraveling the connection between high-order magnetic interactions and local-to-global spin Hamiltonian in non-collinear magnetic dimers},
author = {Ramon Cardias and Jhonatan Santos Silva and Anders Bergman and Attila Szilva and Yaroslav O. Kvashnin and Jonas Fransson and Angela B. Klautau and Olle Eriksson and Anna Delin and Lars Nordström},
url = {https://arxiv.org/abs/2306.07222},
doi = {10.48550/arXiv.2306.07222},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
abstract = {A spin Hamiltonian, which characterizes interatomic interactions between spin moments, is highly valuable in predicting and comprehending the magnetic properties of materials. A deeper understanding of the microscopic origin of magnetic interactions can open new pathways toward realizing nanometer-scale systems for future spintronic devices. Here, we explore a method for explicitly calculating interatomic exchange interactions in non-collinear configurations of magnetic materials considering only a bilinear spin Hamiltonian in a local scenario. Based on density-functional theory (DFT) calculations of dimers adsorbed on metallic surfaces, and with a focus on the Dzyaloshinskii-Moriya interaction (DMI) which is essential for stabilizing chiral non-collinear magnetic states, we discuss the interpretation of the DMI when decomposed into microscopic electron and spin densities and currents. We clarify the distinct origins of spin currents induced in the system and their connection to the DMI. In addition, we reveal how non-collinearity affects the usual DMI, which is solely induced by spin-orbit coupling, and DMI-like interactions brought about by non-collinearity. We explain how the dependence of the DMI on the magnetic configuration establishes a connection between high-order magnetic interactions, enabling the transition from a local to a global spin Hamiltonian.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
A spin Hamiltonian, which characterizes interatomic interactions between spin moments, is highly valuable in predicting and comprehending the magnetic properties of materials. A deeper understanding of the microscopic origin of magnetic interactions can open new pathways toward realizing nanometer-scale systems for future spintronic devices. Here, we explore a method for explicitly calculating interatomic exchange interactions in non-collinear configurations of magnetic materials considering only a bilinear spin Hamiltonian in a local scenario. Based on density-functional theory (DFT) calculations of dimers adsorbed on metallic surfaces, and with a focus on the Dzyaloshinskii-Moriya interaction (DMI) which is essential for stabilizing chiral non-collinear magnetic states, we discuss the interpretation of the DMI when decomposed into microscopic electron and spin densities and currents. We clarify the distinct origins of spin currents induced in the system and their connection to the DMI. In addition, we reveal how non-collinearity affects the usual DMI, which is solely induced by spin-orbit coupling, and DMI-like interactions brought about by non-collinearity. We explain how the dependence of the DMI on the magnetic configuration establishes a connection between high-order magnetic interactions, enabling the transition from a local to a global spin Hamiltonian.
