具有室温铁磁性的二维Janus钛硫属化物  

Room-Temperature Ferromagnetism in Two-Dimensional Janus Titanium Chalcogenides

作　　者：张凯 武晓君[1,2] Zhang Kai;Wu Xiaojun(School of Chemistry and Materials Sciences,University of Science and Technology of China,Hefei 230026;Hefei National Research Center for Physical Sciences at the Microscale,University of Science and Technology of China,Hefei 230026)

机构地区：[1]中国科学技术大学化学与材料科学学院,合肥230026 [2]中国科学技术大学、合肥微尺度物质科学国家研究中心,合肥230026

出　　处：《化学学报》2023年第9期1142-1147,共6页Acta Chimica Sinica

基　　金：国家自然科学基金(Nos.22073087,12147105,22225301)资助。

摘　　要：设计具有室温磁性的二维铁磁材料是发展纳米尺度自旋电子学器件的重要基础,但目前实验合成的二维室温铁磁体种类有限且鲜有报道如何从非磁材料设计室温铁磁体.受近期实验合成JanusMo SSe单层结构的启发,基于第一性原理计算理论预测了一类具有新奇电子结构的二维室温铁磁体Janus TiXY (X=S、Se和Te;Y=H和F).声子谱计算和分子动力学模拟表明这些Janus单层材料具有晶格动力学和热力学稳定性.基于HSE06杂化泛函计算能带结构给出单层TiTeH和TiTeF是带隙为0.18和0.48eV的双极磁性半导体,其中TiTeH由于存在巨磁能带结构效应可以通过将自旋取向由面外翻转至面内实现能带交错-打开转变和自旋分裂调控,即达到自旋取向调控能带结构.单层TiSH、TiSeH、TiSF和TiSeF分别是自旋带隙为2.67、1.73、3.11和2.27eV的铁磁半金属材料.蒙特卡洛模拟给出TiXH和TiXF的居里温度范围分别为339~401 K和341~497 K,表明这些Janus单层材料均具有室温铁磁性.我们还发现在双层TiSF中存在与双层CrI_(3)类似的堆积取向依附的层间磁耦合基态.此外当选用石墨烯作为保护层与TiXY形成异质结后单层Janus结构的本征电子结构特征可以保留.室温铁磁性以及丰富且可调控的电子结构使JanusTi XY材料成为一类理想的自旋电子学候选材料,同时基于非磁材料构建Janus结构为设计新型二维铁磁体开辟了一条崭新途径.Design of two-dimensional(2D)ferromagnetic materials with room-temperature magnetism is basic cornerstone for developing nanoscale spintronics.However,the experimental realized room-temperature ferromagnets are very limited and the design of room-temperature ferromagnets based on non-magnetic materials is rarely reported.Motivated by recently synthesized Janus MoSSe monolayer,we have predicted that Janus TiXY(X=S,Se and Te;Y=H and F)monolayers are intrinsic 2D ferromagnetic materials with above room-temperature long-range spin ordering and diverse electronic structures based on systematically first-principles calculations.The six Janus TiXY monolayers tend to adopt T-phase symmetry.The dynamically and thermally stability of lattice are confirmed by phonon spectrum calculations and molecular dynamics simulations.Band structure calculations at HSE06 functional level demonstrate that the monolayer TiTeH and TiTeF are bipolar ferromagnetic semiconductors(BMS)with bandgap of 0.18 and 0.48 eV,respectively.Further,the spin direction-controlled band crossing to band gaped transition and tunable spin splitting atΓ-point are observed in TiTeH monolayer after flipping the spin orientation along from out-of-plane to in-plane direction owing to giant magneto band-structure effect.The TiSH,TiSeH,TeSF,and TiSeF monolayers are half-metallic ferromagnets(HMF)with a large spin gap of 2.67,1.73,3.11,and 2.27 eV,respectively.Especially,the estimated Curie temperature(T_(c))of TiXH and TiXF based on Monte Carlo simulations are range from 339~401 K and 341~497 K,respectively,which are higher than room-temperature.Similar to bilayer CrI_(3),we also find a stacking configuration dependent interlayer magnetic coupling ground state in bilayer TiSF.Moreover,taking TiSH and TiSF as prototypes,the intrinsic electronic properties can be maintained after the formation of heterojunctions by applying a protective coating graphene layer.The intrinsic room-temperature ferromagnetism together with diverse electronic structures,making the Janus TiX

关 键 词：Janus单层材料 第一性原理 室温铁磁性 电子结构 异质结 

分 类 号：TB34[一般工业技术—材料科学与工程]