We have grown underdoped （х = 0.11, 0.12） and optimally doped （x = 0.16）La2-хSrхCuO4 single crystals by the traveling-solvent floating-zone technique.In order to prepare good quality cuprate crystals,we have ma...We have grown underdoped （х = 0.11, 0.12） and optimally doped （x = 0.16）La2-хSrхCuO4 single crystals by the traveling-solvent floating-zone technique.In order to prepare good quality cuprate crystals,we have made much effort to optimize the preparation procedures.For example,we haveadopted the sol-gel route to prepare a highly fine and homogeneous La2-хSrхCuO4 precursor powder for fabricating a very dense ceramic feed rod used for the floating-zone growth,and we have also used quite a slow growth rate. The high quality of the grown crystals has been verified by double-crystal x-ray rocking curves,with the full-width-at-half-maximum being only 113-150 arcseconds, which are the best data reported so far for La2-хSrхCuO4 crystals.The superconducting critical temperatures of the grown crystals are 30, 31 and 38.5 K for х = 0.11, 0.12 and 0.16 samples, respectively,according to magnetic measurements.展开更多
The present work is concerned with the growth of small-diameter single intermetallic compound crystals by the floating-zone method using a radio frequency(RF)induction heating.In order to maintain a convex solidificat...The present work is concerned with the growth of small-diameter single intermetallic compound crystals by the floating-zone method using a radio frequency(RF)induction heating.In order to maintain a convex solidification interface,which is required for the growth of single crystals,we have developed a novel two-phase inductor comprising a secondary coil,which is short-circuited through capacitor and resistor.The former is adjusted to have resonance in the secondary circuit,which results in a 90 degrees phase lag of the secondary current relative to the primary one.However, it is not always possible to tune the secondary circuit into the resonance as it turns out to be incompatible with the operation of contemporary self-tuning RF-generators.We show that the resonance frequency is unstable unless the resistance of the secondary circuit is made high enough.Analytical results are confirmed by both numerical simulation of the circuit system using the Simulink and measurements on the floating-zone crystal growth facility equipped with a two-phase inductor.展开更多
The magnetic damping effect of the non-uniform magnetic field on the floating-zone crystal growth process in microgravity is studied by numerical simulation. The results show that the non-uni-form magnetic field with ...The magnetic damping effect of the non-uniform magnetic field on the floating-zone crystal growth process in microgravity is studied by numerical simulation. The results show that the non-uni-form magnetic field with designed configuration can effectively reduce the flow near the free surface and then in the melt zone. At the same time, the designed magnetic field can improve the impurity concen-tration non-uniformity along the solidification interface. The primary principles of the magnetic field con-figuration design are also discussed.展开更多
The single crystal of cubic perovskite BaFeO3 shows multiple magnetic transitions and external stimulus sensitive magnetism.In this paper,a 5%-Co-doped BaFeO_(3)(i.e.BaFe_(0.95)Co_(0.05)O_(3))single crystal was grown ...The single crystal of cubic perovskite BaFeO3 shows multiple magnetic transitions and external stimulus sensitive magnetism.In this paper,a 5%-Co-doped BaFeO_(3)(i.e.BaFe_(0.95)Co_(0.05)O_(3))single crystal was grown by combining floating zone methods with high-pressure techniques.Such a slight Co doping has little effect on crystal structure,but significantly changes the magnetism from the parent antiferromagnetic ground state to a ferromagnetic one with the Curie temperature TC≈120 K.Compared with the parent BaFeO3 at the induced ferromagnetic state,the saturated magnetic moment of the doped BaFe_(0.95)Co_(0.05)O_(3) increases by about 10%and reaches 3.64μB/f.u.Resistivity and specific heat measurements show that the ferromagnetic ordering favors metallic-like electrical transport behavior for BaFe_(0.95)Co_(0.05)O_(3).The present work indicates that Co-doping is an effective method to tune the magnetic and electric properties for the cubic perovskite phase of BaFeO_(3).展开更多
基金Project supported by the State Key Development Program for Basic Research of China (Grant No 2006CB0L0302)the National Natural Science Foundation of China (Grant No 10574149)
文摘We have grown underdoped （х = 0.11, 0.12） and optimally doped （x = 0.16）La2-хSrхCuO4 single crystals by the traveling-solvent floating-zone technique.In order to prepare good quality cuprate crystals,we have made much effort to optimize the preparation procedures.For example,we haveadopted the sol-gel route to prepare a highly fine and homogeneous La2-хSrхCuO4 precursor powder for fabricating a very dense ceramic feed rod used for the floating-zone growth,and we have also used quite a slow growth rate. The high quality of the grown crystals has been verified by double-crystal x-ray rocking curves,with the full-width-at-half-maximum being only 113-150 arcseconds, which are the best data reported so far for La2-хSrхCuO4 crystals.The superconducting critical temperatures of the grown crystals are 30, 31 and 38.5 K for х = 0.11, 0.12 and 0.16 samples, respectively,according to magnetic measurements.
文摘The present work is concerned with the growth of small-diameter single intermetallic compound crystals by the floating-zone method using a radio frequency(RF)induction heating.In order to maintain a convex solidification interface,which is required for the growth of single crystals,we have developed a novel two-phase inductor comprising a secondary coil,which is short-circuited through capacitor and resistor.The former is adjusted to have resonance in the secondary circuit,which results in a 90 degrees phase lag of the secondary current relative to the primary one.However, it is not always possible to tune the secondary circuit into the resonance as it turns out to be incompatible with the operation of contemporary self-tuning RF-generators.We show that the resonance frequency is unstable unless the resistance of the secondary circuit is made high enough.Analytical results are confirmed by both numerical simulation of the circuit system using the Simulink and measurements on the floating-zone crystal growth facility equipped with a two-phase inductor.
基金the Project 95-yu-34 of the Ministry of Science and Technology of China the National Natural Science Foundation of China (Grant No. 19789201) .
文摘The magnetic damping effect of the non-uniform magnetic field on the floating-zone crystal growth process in microgravity is studied by numerical simulation. The results show that the non-uni-form magnetic field with designed configuration can effectively reduce the flow near the free surface and then in the melt zone. At the same time, the designed magnetic field can improve the impurity concen-tration non-uniformity along the solidification interface. The primary principles of the magnetic field con-figuration design are also discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11934017 and 11921004)the National Key Research and Development Program of China(Grant Nos.2021YFA1400300,2018YFE0103200,and 2018YFA0305700)+1 种基金the Beijing Natural Science Foundation(Grant No.Z200007)the Fund from the Chinese Academy of Sciences(Grant No.XDB33000000).
文摘The single crystal of cubic perovskite BaFeO3 shows multiple magnetic transitions and external stimulus sensitive magnetism.In this paper,a 5%-Co-doped BaFeO_(3)(i.e.BaFe_(0.95)Co_(0.05)O_(3))single crystal was grown by combining floating zone methods with high-pressure techniques.Such a slight Co doping has little effect on crystal structure,but significantly changes the magnetism from the parent antiferromagnetic ground state to a ferromagnetic one with the Curie temperature TC≈120 K.Compared with the parent BaFeO3 at the induced ferromagnetic state,the saturated magnetic moment of the doped BaFe_(0.95)Co_(0.05)O_(3) increases by about 10%and reaches 3.64μB/f.u.Resistivity and specific heat measurements show that the ferromagnetic ordering favors metallic-like electrical transport behavior for BaFe_(0.95)Co_(0.05)O_(3).The present work indicates that Co-doping is an effective method to tune the magnetic and electric properties for the cubic perovskite phase of BaFeO_(3).
