We theoretically investigate the propagation characteristics of spin waves in skyrmion-based magnonic crystals. It is found that the dispersion relation can be manipulated by strains through magneto-elastic coupling. ...We theoretically investigate the propagation characteristics of spin waves in skyrmion-based magnonic crystals. It is found that the dispersion relation can be manipulated by strains through magneto-elastic coupling. Especially, the allowed bands and forbidden bands in dispersion relations shift to higher frequency with strain changing from compressive to tensile,while shifting to lower frequency with strain changing from tensile to compressive. We also confirm that the spin wave with specific frequency can pass the magnonic crystal or be blocked by tuning the strains. The result provides an advanced platform for studying the tunable skyrmion-based spin wave devices.展开更多
Fe-doped GaN thin films are grown on c-sapphires by metal organic chemical vapour deposition method （MOCVD） Crystalline quality and phase purity are characterized by x-ray diffraction and Raman scattering measuremen...Fe-doped GaN thin films are grown on c-sapphires by metal organic chemical vapour deposition method （MOCVD） Crystalline quality and phase purity are characterized by x-ray diffraction and Raman scattering measurements. There are no detectable second phases formed during growth and no significant degradation in crystalline quality as Fe ions are doped. Fe-related optical transitions are observed in photoluminescence spectra. Magnetic measurements reveal that the films show room-temperature ferromagnetic behaviour. The ferromagnetism may originate from carrier-mediated Fe-doped GaN diluted magnetic semiconductors or nanoscale iron clusters and FeN compounds which we have not detected.展开更多
Zn1-xNixO （x = 0.001, 0.01, 0.02, 0.05 and 0.20） powders are prepared by sol-gel method. An extended x-ray absorption fine structure technique （EXAFS） for the Ni K.edge is employed to probe the local structures ar...Zn1-xNixO （x = 0.001, 0.01, 0.02, 0.05 and 0.20） powders are prepared by sol-gel method. An extended x-ray absorption fine structure technique （EXAFS） for the Ni K.edge is employed to probe the local structures around Ni atoms doped in ZnO powders by fluorescence mode. The near edge EXAFS of the samples does not change in the range of Ni concentration from x = 0.001 to 0.05, which is consistent with the results of x-ray diffraction of the samples. The simulation results for the first shell EXAFS signals indicated that Ni atoms are substituted in Zn sites.展开更多
Single crystals of 4SC（NH2）2–Ni1-xCux Cl2（x = 0.03）（Cu-DTN） containing spin S = 1/2 Cu^2＋and S = 1 Ni^2＋cations are synthesized by slow evaporation methods. Structural characterization demonstrates that the C...Single crystals of 4SC（NH2）2–Ni1-xCux Cl2（x = 0.03）（Cu-DTN） containing spin S = 1/2 Cu^2＋and S = 1 Ni^2＋cations are synthesized by slow evaporation methods. Structural characterization demonstrates that the Cu-DTN is of a tetrahedral structure with lattice parameter c being 9.0995 A, which is 1.32% expansion compared with that of parent material DTN due to the larger radius of the Cu ion. Direct current（DC） susceptibility measurements show that both the antiferromagnetic exchange interaction at low temperature and the large anisotropy of susceptibilities are suppressed after doping the Cu ion, which could be related to the structural distortion and the increase of the super-exchange paths in Cu-DTN.展开更多
Mn-doped GaN epitaxial films were grown by metal organic chemical vapour deposition （MOCVD）. Microstructural properties of films are investigated using Raman scattering. It is found that with increasing Mn-dopants l...Mn-doped GaN epitaxial films were grown by metal organic chemical vapour deposition （MOCVD）. Microstructural properties of films are investigated using Raman scattering. It is found that with increasing Mn-dopants levels, longitudinal optical phonon mode A1 （LO） of films is broadened and shifted towards lower frequency. This phenomenon possibly derives from the difference in bonding strength between Ga-N pairs and Mn-N pairs in host lattice. In addition, optical properties of films are investigated using cathodoluminescence and absorption spectroscopy. Mn-related both emission band around 3.0eV and absorption bands around 1.5 and 2.95eV are observed. By studies on structural and optical properties of Mn-doped GaN, we find that Mn ions substitute for Ga sites in host lattice. However, carrier-mediated ferromagnetic exchange seems unlikely due to deep levels of Mn acceptors.展开更多
Dispersion characteristics of magnonic crystals have attracted considerable attention because of the potential applications for spin-wave devices.In this work,we investigated the strain-manipulated dispersion characte...Dispersion characteristics of magnonic crystals have attracted considerable attention because of the potential applications for spin-wave devices.In this work,we investigated the strain-manipulated dispersion characteristics of magnonic crystals with Dzyaloshinskii–Moriya interaction(DMI)and discussed the potential applications in spin-wave devices.Here,the ground states and stabilities of the magnonic crystals were investigated.Then,the strain-manipulated dispersion characteristics of the magnonic crystals based on domains and skyrmions were studied.The simulation results indicated that,the applied strain could manipulate the band widths and the positions of the allowed frequency bands.Finally,the realization of magnonic crystal heterojunctions and potential applications in spin-wave devices,such as filters,diodes,and transistors based on strain-manipulated magnonic crystals were proposed.Our research provides a theoretical foundation for designing tunable spin-wave devices based on strain-manipulated magnonic crystals with DMI.展开更多
文摘We theoretically investigate the propagation characteristics of spin waves in skyrmion-based magnonic crystals. It is found that the dispersion relation can be manipulated by strains through magneto-elastic coupling. Especially, the allowed bands and forbidden bands in dispersion relations shift to higher frequency with strain changing from compressive to tensile,while shifting to lower frequency with strain changing from tensile to compressive. We also confirm that the spin wave with specific frequency can pass the magnonic crystal or be blocked by tuning the strains. The result provides an advanced platform for studying the tunable skyrmion-based spin wave devices.
基金Supported by the National Basic Research Programme of China under Grant Nos 2006CB604905 and 2006CB604907, the National Hi-Tech Research and Development Programme of China under Grant Nos 2006AA03A142 and 2006AA03Z411, the National Natural Science Foundation of China under Grant Nos 60731160628, 60776001 and 60421003, the Fund of Ministry of Education of China （10416）, and the Natural Science Foundation of Jiangsu Province （BK2005210）.
文摘Fe-doped GaN thin films are grown on c-sapphires by metal organic chemical vapour deposition method （MOCVD） Crystalline quality and phase purity are characterized by x-ray diffraction and Raman scattering measurements. There are no detectable second phases formed during growth and no significant degradation in crystalline quality as Fe ions are doped. Fe-related optical transitions are observed in photoluminescence spectra. Magnetic measurements reveal that the films show room-temperature ferromagnetic behaviour. The ferromagnetism may originate from carrier-mediated Fe-doped GaN diluted magnetic semiconductors or nanoscale iron clusters and FeN compounds which we have not detected.
基金Supported by the Special Fund for Major State Basic Research Project of China under Grant No G2000068305, the National Natural Science Foundation of China under Grant 60390072, and the Natural Science Foundation of Jiangsu Province （BK2005210）.
文摘Zn1-xNixO （x = 0.001, 0.01, 0.02, 0.05 and 0.20） powders are prepared by sol-gel method. An extended x-ray absorption fine structure technique （EXAFS） for the Ni K.edge is employed to probe the local structures around Ni atoms doped in ZnO powders by fluorescence mode. The near edge EXAFS of the samples does not change in the range of Ni concentration from x = 0.001 to 0.05, which is consistent with the results of x-ray diffraction of the samples. The simulation results for the first shell EXAFS signals indicated that Ni atoms are substituted in Zn sites.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11404316 and 11304159)the Natural Science Foundation of Jiangsu Province+2 种基金Chinathe Science Foundation of Nanjing University of Posts and TelecommunicationsChina(Grant Nos.BK20140863 and NY213075)
文摘Single crystals of 4SC（NH2）2–Ni1-xCux Cl2（x = 0.03）（Cu-DTN） containing spin S = 1/2 Cu^2＋and S = 1 Ni^2＋cations are synthesized by slow evaporation methods. Structural characterization demonstrates that the Cu-DTN is of a tetrahedral structure with lattice parameter c being 9.0995 A, which is 1.32% expansion compared with that of parent material DTN due to the larger radius of the Cu ion. Direct current（DC） susceptibility measurements show that both the antiferromagnetic exchange interaction at low temperature and the large anisotropy of susceptibilities are suppressed after doping the Cu ion, which could be related to the structural distortion and the increase of the super-exchange paths in Cu-DTN.
基金Supported by the National Basic Research Programme of China under Grant Nos 2006CB604905 and 2006CB604907, the National Hi-Tech Research Programme of China under Grant No 2006AA03Z411, the National Natural Science Foundation of China under Grant Nos 60721063, 60731160628 and 60820106003.
文摘Mn-doped GaN epitaxial films were grown by metal organic chemical vapour deposition （MOCVD）. Microstructural properties of films are investigated using Raman scattering. It is found that with increasing Mn-dopants levels, longitudinal optical phonon mode A1 （LO） of films is broadened and shifted towards lower frequency. This phenomenon possibly derives from the difference in bonding strength between Ga-N pairs and Mn-N pairs in host lattice. In addition, optical properties of films are investigated using cathodoluminescence and absorption spectroscopy. Mn-related both emission band around 3.0eV and absorption bands around 1.5 and 2.95eV are observed. By studies on structural and optical properties of Mn-doped GaN, we find that Mn ions substitute for Ga sites in host lattice. However, carrier-mediated ferromagnetic exchange seems unlikely due to deep levels of Mn acceptors.
文摘Dispersion characteristics of magnonic crystals have attracted considerable attention because of the potential applications for spin-wave devices.In this work,we investigated the strain-manipulated dispersion characteristics of magnonic crystals with Dzyaloshinskii–Moriya interaction(DMI)and discussed the potential applications in spin-wave devices.Here,the ground states and stabilities of the magnonic crystals were investigated.Then,the strain-manipulated dispersion characteristics of the magnonic crystals based on domains and skyrmions were studied.The simulation results indicated that,the applied strain could manipulate the band widths and the positions of the allowed frequency bands.Finally,the realization of magnonic crystal heterojunctions and potential applications in spin-wave devices,such as filters,diodes,and transistors based on strain-manipulated magnonic crystals were proposed.Our research provides a theoretical foundation for designing tunable spin-wave devices based on strain-manipulated magnonic crystals with DMI.
