Lead zirconate(PbZrO_(3))is considered the prototypical antiferroelectric material with an antipolar ground state.Yet,several experimental and theoretical works hint at a partially polar behaviour in this compound,ind...Lead zirconate(PbZrO_(3))is considered the prototypical antiferroelectric material with an antipolar ground state.Yet,several experimental and theoretical works hint at a partially polar behaviour in this compound,indicating that the polarization may not be completely compensated.In this work,we propose a simple ferrielectric structure for lead zirconate.First-principles calculations reveal this state to be more stable than the commonly accepted antiferroelectric phase at low temperatures,possibly up to room temperature,suggesting that PbZrO_(3)may not be antiferroelectric at ambient conditions.We discuss the implications of our discovery,how it can be reconciled with experimental observations and how the ferrielectric phase could be obtained in practice.展开更多
Multiferroics in which giant ferroelectric polarization and magnetism coexist are of tremendous potential for engineering disruptive applications in information storage and energy conversion.Yet the functional propert...Multiferroics in which giant ferroelectric polarization and magnetism coexist are of tremendous potential for engineering disruptive applications in information storage and energy conversion.Yet the functional properties of multiferroics are thought to be affected detrimentally by the presence of point defects,which may be abundant due to the volatile nature of some constituent atoms and the high temperatures involved in the synthesis of materials.Here,we demonstrate with theoretical methods that oxygen vacancies may enhance the functionality of multiferroics by radically changing their magnetic interactions in thin films.Specifically,oxygen vacancies may restore missing magnetic super-exchange interactions in large axial ratio phases,leading to full antiferromagnetic spin ordering,and induce the stabilization of ferrimagnetic states with considerable net magnetizations.Our theoretical study should help to clarify the origins of long-standing controversies in bismuth ferrite and improve the design of technological applications based on multiferroics.展开更多
Perovskite oxides offer tremendous potential for applications in information storage and energy conversion,owing to a subtle interplay between their spin,charge,orbital and lattice degrees of freedom.Here,we further e...Perovskite oxides offer tremendous potential for applications in information storage and energy conversion,owing to a subtle interplay between their spin,charge,orbital and lattice degrees of freedom.Here,we further expand the possible range of perovskite oxides operation towards the fields of thermal management and thermal computing by exploiting an exceptional synergy between different ferroic orders.We propose dynamical control of the heat flow in a distinctive family of perovskite oxides obtained via the application of small electric(~10 kV/cm)and/or magnetic(~1 T)fields.Based on first-principles simulations,we predict a relative heat conductivity variation of~100%in SrMnO_(3) thin films near room temperature resulting from a phase transition that involves huge changes in both the magnetization and electric polarization.The disclosed giant multiphononic effects are fundamentally caused by anharmonic spin-phonon couplings that strongly influence the mean lifetime of phonons.展开更多
Half-metallicity(HM)offers great potential for engineering spintronic applications,yet only few magnetic materials present metallicity in just one spin channel.In addition,most HM systems become magnetically disordere...Half-metallicity(HM)offers great potential for engineering spintronic applications,yet only few magnetic materials present metallicity in just one spin channel.In addition,most HM systems become magnetically disordered at temperatures well below ambient conditions,which further hinders the development of spin-based electronic devices.Here,we use first-principles methods based on density functional theory(DFT)to investigate the electronic,magnetic,structural,mixing,and vibrational properties of 90 XYZ half-Heusler(HH)alloys(X=Li,Na,K,Rb,Cs;Y=V,Nb,Ta;Z=Si,Ge,Sn,S,Se,Te).We disclose a total of 28 new HH compounds that are ferromagnetic,vibrationally stable,and HM,with semiconductor band gaps in the range of 1-4 eV and HM band gaps of 0.2-0.8 eV.By performing Monte Carlo simulations of a spin Heisenberg model fitted to DFT energies,we estimate the Curie temperature,T_(C),of each HM compound.We find that 17 HH HM remain magnetically ordered at and above room temperature,namely,300≤T_(C)≤450 K,with total magnetic moments of 2 and 4 mB.A further materials sieve based on zero-temperature mixing energies let us to conclude 5 overall promising HH HM that remain magnetically ordered at and above room temperature:NaVSi,RbVTe,CsVS,CsVSe,and RbNbTe.We also predict 2 semiconductor materials that are ferromagnetic at ambient conditions:LiVSi and LiVGe.展开更多
Due to its high energy efficiency and environmental friendliness,solid-state cooling based on the barocaloric(BC)effect represents a promising alternative to traditional refrigeration technologies relying on greenhous...Due to its high energy efficiency and environmental friendliness,solid-state cooling based on the barocaloric(BC)effect represents a promising alternative to traditional refrigeration technologies relying on greenhouse gases.Plastic crystals displaying orientational order-disorder solid-solid phase transitions have emerged among the most gifted materials on which to realize the full potential of BC solid-state cooling.However,a comprehensive understanding of the atomistic mechanisms on which order-disorder BC effects are sustained is still missing,and rigorous and systematic methods for quantitatively evaluating and anticipating them have not been yet established.展开更多
基金H.A.and J.Í.acknowledge funding by the Luxembourg National Research Fund through the project INTER/ANR/16/11562984/EXPAND/KreiselC.C.acknowledges support from the Spanish Ministry of Science,Innovation and Universities under the“Ramón y Cajal”fellowship RYC2018-024947-1+3 种基金I.M.S.acknowledges the support of Ministerio de Economía,Industria y Competitividad(MINECO-Spain)through Grant No.PID2019-108573GB-C22Severo Ochoa FUNFUTURE centre of excellence(CEX2019-000917-S)of Generalitat de Catalunya(Grant No.2017 SGR1506)of the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation programme(Grant Agreement No.724529).
文摘Lead zirconate(PbZrO_(3))is considered the prototypical antiferroelectric material with an antipolar ground state.Yet,several experimental and theoretical works hint at a partially polar behaviour in this compound,indicating that the polarization may not be completely compensated.In this work,we propose a simple ferrielectric structure for lead zirconate.First-principles calculations reveal this state to be more stable than the commonly accepted antiferroelectric phase at low temperatures,possibly up to room temperature,suggesting that PbZrO_(3)may not be antiferroelectric at ambient conditions.We discuss the implications of our discovery,how it can be reconciled with experimental observations and how the ferrielectric phase could be obtained in practice.
文摘Multiferroics in which giant ferroelectric polarization and magnetism coexist are of tremendous potential for engineering disruptive applications in information storage and energy conversion.Yet the functional properties of multiferroics are thought to be affected detrimentally by the presence of point defects,which may be abundant due to the volatile nature of some constituent atoms and the high temperatures involved in the synthesis of materials.Here,we demonstrate with theoretical methods that oxygen vacancies may enhance the functionality of multiferroics by radically changing their magnetic interactions in thin films.Specifically,oxygen vacancies may restore missing magnetic super-exchange interactions in large axial ratio phases,leading to full antiferromagnetic spin ordering,and induce the stabilization of ferrimagnetic states with considerable net magnetizations.Our theoretical study should help to clarify the origins of long-standing controversies in bismuth ferrite and improve the design of technological applications based on multiferroics.
基金We acknowledge financial support by MCIN/AEI/10.13039/501100011033 under grant PID2020-119777GB-I00the Ramón y Cajal fellowship RYC2018-024947-I+2 种基金the Severo Ochoa Centres of Excellence Program(CEX2019-000917-S)the Generalitat de Catalunya under grant no.and 2017 SGR 1506Calculations were performed at the Centro de Supercomputación de Galicia(CESGA)within action FI-2022-1-0012 of the Red Española de Supercomputación(RES).We also thank the support of the Luxembourg National Research Fund through project FNR/C18/MS/12705883/REFOX(J.Í.).
文摘Perovskite oxides offer tremendous potential for applications in information storage and energy conversion,owing to a subtle interplay between their spin,charge,orbital and lattice degrees of freedom.Here,we further expand the possible range of perovskite oxides operation towards the fields of thermal management and thermal computing by exploiting an exceptional synergy between different ferroic orders.We propose dynamical control of the heat flow in a distinctive family of perovskite oxides obtained via the application of small electric(~10 kV/cm)and/or magnetic(~1 T)fields.Based on first-principles simulations,we predict a relative heat conductivity variation of~100%in SrMnO_(3) thin films near room temperature resulting from a phase transition that involves huge changes in both the magnetization and electric polarization.The disclosed giant multiphononic effects are fundamentally caused by anharmonic spin-phonon couplings that strongly influence the mean lifetime of phonons.
基金supported under the Australian Research Council’s Future Fellowship funding scheme(No.FT140100135)financial support from the Higher Education Commission(HEC)of Pakistan under the IRSIP scholarship(PIN:IRSIP 35 PSc 11).
文摘Half-metallicity(HM)offers great potential for engineering spintronic applications,yet only few magnetic materials present metallicity in just one spin channel.In addition,most HM systems become magnetically disordered at temperatures well below ambient conditions,which further hinders the development of spin-based electronic devices.Here,we use first-principles methods based on density functional theory(DFT)to investigate the electronic,magnetic,structural,mixing,and vibrational properties of 90 XYZ half-Heusler(HH)alloys(X=Li,Na,K,Rb,Cs;Y=V,Nb,Ta;Z=Si,Ge,Sn,S,Se,Te).We disclose a total of 28 new HH compounds that are ferromagnetic,vibrationally stable,and HM,with semiconductor band gaps in the range of 1-4 eV and HM band gaps of 0.2-0.8 eV.By performing Monte Carlo simulations of a spin Heisenberg model fitted to DFT energies,we estimate the Curie temperature,T_(C),of each HM compound.We find that 17 HH HM remain magnetically ordered at and above room temperature,namely,300≤T_(C)≤450 K,with total magnetic moments of 2 and 4 mB.A further materials sieve based on zero-temperature mixing energies let us to conclude 5 overall promising HH HM that remain magnetically ordered at and above room temperature:NaVSi,RbVTe,CsVS,CsVSe,and RbNbTe.We also predict 2 semiconductor materials that are ferromagnetic at ambient conditions:LiVSi and LiVGe.
基金supported by the MINECO Projects PID2020-112975GB-I00 and TED2021-130265B-C22(Spain)by the DGU Project 2021SGR-00343(Catalonia)+2 种基金C.C.acknowledges financial support from the Spanish Ministry of Science,Innovation and Universities under the“Ramón y Cajal”fellowship RYC2018-024947-IC.E.-S.acknowledges financial support from the Spanish Ministry of Science,Innovation and Universities under the“Becas Margarita Salas para la formación de doctores jóvenes”fellowship 2021UPC-MS-67395Additional computational support was provided by the Red Española de Supercomputación(RES)under the grants FI-2022-1-0006,FI-2022-2-0003 and FI-2022-3-0014.
文摘Due to its high energy efficiency and environmental friendliness,solid-state cooling based on the barocaloric(BC)effect represents a promising alternative to traditional refrigeration technologies relying on greenhouse gases.Plastic crystals displaying orientational order-disorder solid-solid phase transitions have emerged among the most gifted materials on which to realize the full potential of BC solid-state cooling.However,a comprehensive understanding of the atomistic mechanisms on which order-disorder BC effects are sustained is still missing,and rigorous and systematic methods for quantitatively evaluating and anticipating them have not been yet established.
