The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hyste...The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hysteresis, of which the critical magnetic fields are temperature-dependent and show anisotropy. By using a pulsed high magnetic field up to 75 T, the magnetization behavior shows that the critical transition magnetic fields of spin- flip/flop shift to lower field regions with an increase in temperature. According to the magnetization curves, a complete magnetic phase diagram is depicted.展开更多
The effects of Mn doping on the microstructure and magnetic properties of CuFeO2 systems were studied using X-ray diffraction(XRD),X-ray photoelectron spectroscopy,scanning electron microscopy(SEM),and a physical prop...The effects of Mn doping on the microstructure and magnetic properties of CuFeO2 systems were studied using X-ray diffraction(XRD),X-ray photoelectron spectroscopy,scanning electron microscopy(SEM),and a physical property measurement method.The microstructure measurements demonstrated that the substitution of Mn for Fe can cause lattice distortion,promote grain growth,and change the valence state of Fe and Mn ions.Ceramic samples with doping content x=0.00−0.03 exhibited two successive magnetic transition temperature(TN)at TN1≈14 K and TN2≈10 K.TN decreased gradually with the Mn4+content,and TN2 was not observed in the x>0.05 samples within a temperature range of T=5−300 K.Magnetic hysteresis loops revealed that only anti-ferromagnetic behavior occurred in the low-doped samples(x=0.00−0.03),and the coexistence of ferromagnetism and anti-ferromagnetism was observed in the high-doped samples(x=0.05−0.10).Besides,the x=0.10 sample had a maximum magnetization of 5.98 emu/g.This study provides basic experimental data for investigating the relationship between the microstructure and magnetic properties of CuFeO2 systems.展开更多
CuFeO2 is a promising photocathode for H2 evolution and CO2 reduction reactions.To better understand the complex defect chemistry and role of impurity phases in this material and their effect on the photochemical perf...CuFeO2 is a promising photocathode for H2 evolution and CO2 reduction reactions.To better understand the complex defect chemistry and role of impurity phases in this material and their effect on the photochemical performance,we employ visible light transient absorption spectroscopy and density functional theory(DFT)calculations to investigate the electron dynamics in electrochemically deposited Cu-Fe oxide thin films.Kinetic analysis of carrier lifetime shows a fast,sub-ps contribution to relaxation followed by persistence of a Iong-lived state to time delays greater than 2 ns.Increasing amplitude of the Iong-lived state is shown to correlate with the rate of fast initial relaxation,and this is explained in terms of a competition between charge carrier trapping and charge separation.Charge separation in CuFeO2 occurs via hole thermalizati on from O 2p to Cu 3d vale nee band states leadi ng to segregatio n of electr ons and holes across layers in the CuFeO2 lattice.Correlation between transient absorption measurements and DFT calculations suggest that Cu vacancies enhanee photochemical performance by facilitating charge separation kinetics.In contrast,O interstitials are predicted to switch the relative positions of O 2p and Cu 3d vale nee band states,which would in hibit charge separatio n by in ter-band hole thermal izatio n.Fin ally,we find no evide nee for electron in jecti on from CuFeO2 to CuO suggest!ng that charge separati on at this heterostructure in terface does not play a role in the carrier lifetime or photochemical performance of the catalysts studied here.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 11104091the Guangxi Key Laboratory of Information Materials of Guilin University of Electronic Technology under Grant No 1210908-05-K
文摘The magnetization behavior of a CuFeO2 single crystal grown by the floating zone technique is investigated with a pulsed high magnetic field. We observe a series of field-induced multi-step-like transitions with hysteresis, of which the critical magnetic fields are temperature-dependent and show anisotropy. By using a pulsed high magnetic field up to 75 T, the magnetization behavior shows that the critical transition magnetic fields of spin- flip/flop shift to lower field regions with an increase in temperature. According to the magnetization curves, a complete magnetic phase diagram is depicted.
基金This study was supported by the National Natural Science Foundation of China(11675149 and 11775192).
文摘The effects of Mn doping on the microstructure and magnetic properties of CuFeO2 systems were studied using X-ray diffraction(XRD),X-ray photoelectron spectroscopy,scanning electron microscopy(SEM),and a physical property measurement method.The microstructure measurements demonstrated that the substitution of Mn for Fe can cause lattice distortion,promote grain growth,and change the valence state of Fe and Mn ions.Ceramic samples with doping content x=0.00−0.03 exhibited two successive magnetic transition temperature(TN)at TN1≈14 K and TN2≈10 K.TN decreased gradually with the Mn4+content,and TN2 was not observed in the x>0.05 samples within a temperature range of T=5−300 K.Magnetic hysteresis loops revealed that only anti-ferromagnetic behavior occurred in the low-doped samples(x=0.00−0.03),and the coexistence of ferromagnetism and anti-ferromagnetism was observed in the high-doped samples(x=0.05−0.10).Besides,the x=0.10 sample had a maximum magnetization of 5.98 emu/g.This study provides basic experimental data for investigating the relationship between the microstructure and magnetic properties of CuFeO2 systems.
基金This work was supported by the National Science Foundation under NSF award number 1665280.We thank Barbara Dunlap for assistance with TA measurements,which were conducted in the Center for Chemical and Biophysical Dynamics at Ohio State University.We thank Yutichai Mueanngern for assistance with TEM measurements,which were performed in the Center for Electron Microscopy and Analysis at Ohio State University.We thank Professor Anne Co for her assistance with the Mott-Schottky analysis.We acknowledge the Ohio Supercomputing Center for providing computational resources.
文摘CuFeO2 is a promising photocathode for H2 evolution and CO2 reduction reactions.To better understand the complex defect chemistry and role of impurity phases in this material and their effect on the photochemical performance,we employ visible light transient absorption spectroscopy and density functional theory(DFT)calculations to investigate the electron dynamics in electrochemically deposited Cu-Fe oxide thin films.Kinetic analysis of carrier lifetime shows a fast,sub-ps contribution to relaxation followed by persistence of a Iong-lived state to time delays greater than 2 ns.Increasing amplitude of the Iong-lived state is shown to correlate with the rate of fast initial relaxation,and this is explained in terms of a competition between charge carrier trapping and charge separation.Charge separation in CuFeO2 occurs via hole thermalizati on from O 2p to Cu 3d vale nee band states leadi ng to segregatio n of electr ons and holes across layers in the CuFeO2 lattice.Correlation between transient absorption measurements and DFT calculations suggest that Cu vacancies enhanee photochemical performance by facilitating charge separation kinetics.In contrast,O interstitials are predicted to switch the relative positions of O 2p and Cu 3d vale nee band states,which would in hibit charge separatio n by in ter-band hole thermal izatio n.Fin ally,we find no evide nee for electron in jecti on from CuFeO2 to CuO suggest!ng that charge separati on at this heterostructure in terface does not play a role in the carrier lifetime or photochemical performance of the catalysts studied here.
