We report a comprehensive Raman scattering study on layered MPS_3(M = Mn, Fe, Ni), a two-dimensional magnetic compound with weak van der Waals interlayer coupling. The observed Raman phonon modes have been well assign...We report a comprehensive Raman scattering study on layered MPS_3(M = Mn, Fe, Ni), a two-dimensional magnetic compound with weak van der Waals interlayer coupling. The observed Raman phonon modes have been well assigned by the combination of first-principles calculations and the polarization-resolved spectra. Careful symmetry analysis on the angle-dependent spectra demonstrates that the crystal symmetry is strictly described by C_(2h)but can be simplified to D_(3d) with good accuracy. Interestingly, the three compounds share exactly the same lattice structure but show distinct magnetic structures. This provides us with a unique opportunity to study the effect of different magnetic orders on lattice dynamics in MPS_3. Our results reveal that the in-plane Nel antiferromagnetic(AF) order in MnPS_3 favors a spin–phonon coupling compared to the in-plane zig-zag AF in NiPS_3 and FePS_3. We have discussed the mechanism in terms of the folding of magnetic Brillouin zones. Our results provide insights into the relation between lattice dynamics and magnetism in the layered MPX_3(M = transition metal, X = S, Se) family and shed light on the magnetism of monolayer MPX_3 materials.展开更多
Growth of high-quality single crystals is of great significance for research of condensed matter physics. The exploration of suitable growing conditions for single crystals is expensive and time-consuming, especially ...Growth of high-quality single crystals is of great significance for research of condensed matter physics. The exploration of suitable growing conditions for single crystals is expensive and time-consuming, especially for ternary compounds because of the lack of ternary phase diagram. Here we use machine learning(ML) trained on our experimental data to predict and instruct the growth. Four kinds of ML methods, including support vector machine(SVM), decision tree, random forest and gradient boosting decision tree, are adopted. The SVM method is relatively stable and works well, with an accuracy of 81% in predicting experimental results. By comparison,the accuracy of laboratory reaches 36%. The decision tree model is also used to reveal which features will take critical roles in growing processes.展开更多
The layered magnetic van der Waals materials have generated tremendous interest due to their potential applications and importance in fundamental research.Previous x-ray diffraction(XRD)studies on the magnetic van der...The layered magnetic van der Waals materials have generated tremendous interest due to their potential applications and importance in fundamental research.Previous x-ray diffraction(XRD)studies on the magnetic van der Waals compound VI3,revealed a structural transition above the magnetic transition but output controversial analysis on symmetry.In this paper we carried out polarized Raman scattering measurements on VI3 from 10 K to 300 K,with focus on the two Ag phonon modes at^71.1 cm^-1 and 128.4 cm-1.Our careful symmetry analysis based on the angle-dependent spectra demonstrates that the crystal symmetry can be well described by C2h rather than D3d both above and below structural phase transition.We further performed temperature-dependent Raman experiments to study the magnetism in VI3.Fano asymmetry and anomalous linewidth drop of two Ag phonon modes at low temperatures,point to a significant spin-phonon coupling.This is also supported by the softening of 71.1-cm^-1 mode above the magnetic transition.The study provides the fundamental information on lattice dynamics and clarifies the symmetry in VI3.And spin-phonon coupling existing in a wide temperature range revealed here may be meaningful in applications.展开更多
We study the influence of Cr doping on magnetic properties ofα-RuCl3 single crystals in detail.With increasing Cr content,the c-axial lattice parameter increases gradually,implying that the Cr doping may weaken the i...We study the influence of Cr doping on magnetic properties ofα-RuCl3 single crystals in detail.With increasing Cr content,the c-axial lattice parameter increases gradually,implying that the Cr doping may weaken the interlayer interactions.The magnetism of Ru1-xCrxCl3 single crystals evolves from a long-range AFM order to a possible spin-glass state with Cr doping.The appearance of a possible spin-glass state can be explained by the introduction of FM interaction by Cr3+ions,which competes with the AFM interaction between Ru3+ions.Noreover,the larger magnetic moment of Cr3+ion with S=3/2 than Ru3+ion with Jeff=1/2 also results in a monotonic increase of the effective moment of Ru1-xCrxCl3 single crystal.展开更多
基金Project supported by the Ministry of Science and Technology of China(Grant Nos.2016YFA0300504 and 2017YFA0302904)the National Natural Science Foundation of China(Grant Nos.11474357 and 11774419)the Fundamental Research Funds for the Central Universities,China,and the Research Funds of Renmin University of China(Grant No.14XNLQ03)
文摘We report a comprehensive Raman scattering study on layered MPS_3(M = Mn, Fe, Ni), a two-dimensional magnetic compound with weak van der Waals interlayer coupling. The observed Raman phonon modes have been well assigned by the combination of first-principles calculations and the polarization-resolved spectra. Careful symmetry analysis on the angle-dependent spectra demonstrates that the crystal symmetry is strictly described by C_(2h)but can be simplified to D_(3d) with good accuracy. Interestingly, the three compounds share exactly the same lattice structure but show distinct magnetic structures. This provides us with a unique opportunity to study the effect of different magnetic orders on lattice dynamics in MPS_3. Our results reveal that the in-plane Nel antiferromagnetic(AF) order in MnPS_3 favors a spin–phonon coupling compared to the in-plane zig-zag AF in NiPS_3 and FePS_3. We have discussed the mechanism in terms of the folding of magnetic Brillouin zones. Our results provide insights into the relation between lattice dynamics and magnetism in the layered MPX_3(M = transition metal, X = S, Se) family and shed light on the magnetism of monolayer MPX_3 materials.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0401000 and2017YFA0302901the National Basic Research Program of China under Grant No 2015CB921000+2 种基金the National Natural Science Foundation of China under Grant Nos 11574371,11774399 and 11774398the Beijing Natural Science Foundation(Z180008)the Strategic Priority Research Program of Chinese Academy of Sciences under Grant No XDB28000000
文摘Growth of high-quality single crystals is of great significance for research of condensed matter physics. The exploration of suitable growing conditions for single crystals is expensive and time-consuming, especially for ternary compounds because of the lack of ternary phase diagram. Here we use machine learning(ML) trained on our experimental data to predict and instruct the growth. Four kinds of ML methods, including support vector machine(SVM), decision tree, random forest and gradient boosting decision tree, are adopted. The SVM method is relatively stable and works well, with an accuracy of 81% in predicting experimental results. By comparison,the accuracy of laboratory reaches 36%. The decision tree model is also used to reveal which features will take critical roles in growing processes.
基金Project supported by the Science Fund from the Ministry of Science and Technology of China(Grant Nos.2017YFA0302904 and 2016YFA0300504)the National Natural Science Foundation of China(Grant Nos.11774419,U1932215,11774423,and 11822412)+1 种基金the Fundamental Research Funds for the Central Universities,Chinathe Research Funds of Renmin University of China(RUC)(Grant Nos.15XNLQ07,18XNLG14,and 19XNLG17).
文摘The layered magnetic van der Waals materials have generated tremendous interest due to their potential applications and importance in fundamental research.Previous x-ray diffraction(XRD)studies on the magnetic van der Waals compound VI3,revealed a structural transition above the magnetic transition but output controversial analysis on symmetry.In this paper we carried out polarized Raman scattering measurements on VI3 from 10 K to 300 K,with focus on the two Ag phonon modes at^71.1 cm^-1 and 128.4 cm-1.Our careful symmetry analysis based on the angle-dependent spectra demonstrates that the crystal symmetry can be well described by C2h rather than D3d both above and below structural phase transition.We further performed temperature-dependent Raman experiments to study the magnetism in VI3.Fano asymmetry and anomalous linewidth drop of two Ag phonon modes at low temperatures,point to a significant spin-phonon coupling.This is also supported by the softening of 71.1-cm^-1 mode above the magnetic transition.The study provides the fundamental information on lattice dynamics and clarifies the symmetry in VI3.And spin-phonon coupling existing in a wide temperature range revealed here may be meaningful in applications.
基金Supported by the Fundamental Research Funds for the Central Universities and the Research Funds of Renmin University of China(Grant Nos.15XNLQ07,18XNLG14,and 19XNLG17)。
文摘We study the influence of Cr doping on magnetic properties ofα-RuCl3 single crystals in detail.With increasing Cr content,the c-axial lattice parameter increases gradually,implying that the Cr doping may weaken the interlayer interactions.The magnetism of Ru1-xCrxCl3 single crystals evolves from a long-range AFM order to a possible spin-glass state with Cr doping.The appearance of a possible spin-glass state can be explained by the introduction of FM interaction by Cr3+ions,which competes with the AFM interaction between Ru3+ions.Noreover,the larger magnetic moment of Cr3+ion with S=3/2 than Ru3+ion with Jeff=1/2 also results in a monotonic increase of the effective moment of Ru1-xCrxCl3 single crystal.