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| 1 | Oxygen-vacancy induced magnetic phase transitions in multiferroic thin films显示文摘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. | César Menéndez Dewei Chu Claudio Cazorla | 2020 | npj Computational Materials2020，，1： | 1 |
| 2 | On the possibility that PbZrO_(3) not be antiferroelectric显示文摘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. | Hugo Aramberri Claudio Cazorla Massimiliano Stengel Jorge Íñiguez | 2021 | npj Computational Materials2021，，1： | 0 |
| 3 | First-principles prediction of magnetically ordered half-metals above room temperature显示文摘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. | Muhammad Atif Sattar S.Aftab Ahmad Fayyaz Hussain Claudio Cazorla | 2019 | Journal of Materiomics2019，5，3： | 0 |
| 4 | Giant multiphononic effects in a perovskite oxide显示文摘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. | Claudio Cazorla Massimiliano Stengel JorgeÍñiguez Riccardo Rurali | 2023 | npj Computational Materials2023，，1： | 0 |
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