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- Wang, Duo, et al.
(författare)
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Prediction of half-metallic ferrimagnetic quadruple perovskites ACu(3)Fe(2)Re(2)O(12) (A = Ca, Sr, Ba, Pb, Sc, Y, La) with high Curie temperatures
- 2021
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Ingår i: Physical Review Materials. - : American Physical Society. - 2475-9953. ; 5:5
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Tidskriftsartikel (refereegranskat)abstract
- A- and B-site ordered quadruple perovskites with the chemical formula AA(3)'B2B2'O-12 can form with 1:3 ratio at the A site. A unique feature of this specially ordered perovskite is that three different atomic sites (A', B, and B' sites) can all accommodate magnetic transition metals. As a consequence, multiple magnetic and electronic interactions can occur at A', B, and/or B' sites, giving rise to a series of intriguing physical phenomena. CaCu3Fe2Re2O12 is a good example, which shows half-metallic electronic structure, large magnetization, and a very high Curie temperature. Here we investigated a series of ferrimagnetic (FiM) compounds ACu(3)Fe(2)Re(2)O(12) (A=Ca, Sr, Ba, Pb, Sc, Y, La) by using density functional theory and Monte Carlo simulations. We found that all compounds with A(2+) ions exhibit high Curie temperatures (above 405 K), and the compounds with A(3+) substitution yield even higher T-C (above 502 K). By examining interatomic exchange parameters, we found that the antiferromagnetic exchange couplings between Re and Cu as well as Re and Fe are responsible for this very high Curie temperature. For the compounds with A(3+) substitution, electron doping in bands around the Fermi level dominated by the Re ions strengthens the Re-Cu, Re-Fe, and Re-Re exchange interactions, which cause an increase in the critical temperature. Finally, we calculated the formation energies of the quadruple perovskites with respect to the possible decomposition pathways and have found that the values are reasonable for the synthesis of these compounds under the conditions of high pressure and high temperature. In summary, this work demonstrates a design strategy of enhancing the spin ordering temperature by replacing A-site nonmagnetic ions.
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- Wang, Duo, et al.
(författare)
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Systematic Study of Monolayer to Trilayer CrI3 : Stacking Sequence Dependence of Electronic Structure and Magnetism
- 2021
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:33, s. 18467-18473
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, two-dimensional magnetic materials have attracted a lot of attention due to their unique magnetic properties, which can be manipulated by various degrees of freedom in a van der Waals stacked heterostructure, where different interlayer stackings affect the properties in different ways by exploiting weak interlayer interactions. An interesting example is CrI3, where the interlayer magnetic coupling can be determined by the stacking sequence. Here we present a systematic study of the magnetic properties of monolayer, bilayer, and trilayer CrI3 by using density functional theory and Monte Carlo simulations. The effects of different stacking sequences and the number of layers on the magnetic interaction in multilayer CrI3 have been critically analyzed. We have found that the antiferromagnetic interlayer coupling occurs with specific interlayer shifting, while intralayer exchange interactions increase with the number of layers. It is noteworthy that interlayer interactions are independent of the number of layers, whereas the magnetic ordering temperature rises with the increasing number of layers. Moreover, we present the Curie temperatures obtained from Monte Carlo simulations and adiabatic magnon spectra for all the stacking sequences considered here.
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- Wang, Duo, et al.
(författare)
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Unraveling complex magnetism in two-dimensional FeS2
- 2021
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9950 .- 2469-9969. ; 104:24
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Tidskriftsartikel (refereegranskat)abstract
- Atomically thin two-dimensional (2D) magnets have given rise to emergent phenomena due to magnetic exchange and spin-orbit coupling showing great promise for realizing ultrathin device structures. In this paper, we critically examine the magnetic properties of 2D FeS2, a non van der Waals magnet, which has been recently claimed to exhibit room-temperature ferromagnetism in the (111) orientation. Our ab initio study based on collinear density functional theory has revealed the ground state as an antiferromagnetic one with an ordering temperature of around 100 K along with a signature of spin-phonon coupling, which may trigger a ferromagnetic coupling via strain. Moreover, our calculations based on spin spirals indicate the possibility of noncollinear magnetic structures, which is also supported by Monte Carlo simulations based on ab initio magnetic exchange parameters. This opens up an excellent possibility to manipulate magnetic structures by the application of directional strain.
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