Investigation Of Ferromagnetism In Rhenium Disulfide Nanomaterials

Information storage and security is one of the most important issues that humans are facing.However,traditional devices suffered with many problems,for example,the poor storage capacity.Such situation aroused people’s great attentions.In the past few decades,the spintronics developed fastly and brought light for solving this problems.It is devoted to combining the spin degrees of freedom with integrated electronics to realize the regulation of spin-related devices.Besides,spintronics devices have the advantages of small size,large storage capacity and low energy consumptions,and are regarded as the most promising electronic equipments.Obviously,the realization of any device is depended on the performance of material itself.It was under such background that the TMDs attracted much attentions.Compared with its bulk,the two-dimensional TMDs is not only energy saving but also can meet the requirements of device miniaturization and function maximization,which are considered as the next-generation materials in spintronics.Unfortunately,most TMDs are intrinsically nonmagnetic.Therefore,how to introduce magnetism into TMDs becomes an urgent issue.In this paper,we prepared ReS₂ nanosheets through the hydrothermal method,and the intrinsic room-temperature ferromagnetism was introduced into ReS₂ by the way of transition metal doping and non-metal adsorption.By controlling the experimental parameters（temperature,doping concentrations,annealing time,ect.）,the ferromagnetism of the sample s was adjusted.What’s more,the origin of magnetism was further explored through the first-principles calculations.It provided experimental and theoretical basis for the application of TMDs in spintronic devices.The main contents of this work are as follows:1.The Cr-doped ReS₂（Cr-ReS₂）nanosheets with a series of Cr contents were prepared through the hydrothermal method.Magnetic property measurements show that it behaves an intrinsic room temperature ferromagnetism.Its magnetic signal was strongly enhanced in the low concentrations with the increasing of Cr contents.And the maximum M_S reached to 2.13×10^-3 emu/g.Besides,first-principles calculations further indicated that Cr dopants can provide spin-polarized magnetic moments for the system.As for the magnetic coupling interreactions between different isolated moments,we also gave out a reasonable explanation from the perspective of calculations.2.Based on the ReS₂ nanosheets,the phosphated and fluorinated ReS₂ samples were obtained via an annealing process with a certain temperature and argon atmosphere.And samples with different P（or F）contents were prepared by changing the experimental parameters（dosage of Na H₂PO₂ or NH₄F,distance between the porcelain boats,the annealing time and temperature）.The magnetic measurements demonstrated that the phosphated（or fluorinated）ReS₂ has a certain ferromagnetism,and its magnetic signal can be adjusted by changing the concentrations of P（or F）.Among all the samples,the maximum M_S reached to 0.017 emu/g（or 0.010 emu/g）when the ratios of P stayed at 1.54 at.%（as for F,it is 5.11 at.%）.First-principles calculations indicated that P（or F）atoms tend to be ad sorbed on the ReS₂.Besides the possible defects of the samples,the strong orbital hybridization between P p（or F p）,Re d is the main reason of arising the ferromagnetism.In addition,the calculation results also demonstrated that different magnetic coupling interactions exists in different systems,which well explained the relevant experimental results.