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- 저자 : Shixun Cao (검색결과 6 건)
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Jincang Zhang,Shixun Cao,Ruiying Zhang,Liming Yu,Chao Jing 한국물리학회 2005 Current Applied Physics Vol.5 No.4
Polycrystalline nano-grain-boundary multi-doping ZnO-based nonlinear varistors with higher concentration additives have beenfabricated by solgel and standard solid-state reaction method, of which the best sample has a very high threshold voltage ofEb ¼ 3300 V/mm. The eect of sintering processes, sintering temperature and sintering time, and that of additive concentration ofBi2O3 on Eb of the samples are systematically investigated. The results show that the great merit of solgel method is its highthreshold voltage obtained by a lower sintering temperature than the solid-state reaction method. The present work also shows thatve phases including solid-state sintering, rich Bi liquid phase formation and ZnO as well as other additive dissolution, ZnO graingrowth, the secondary phase sucient formation and evolution have been experienced at dierent sintering temperatures. The holetype defect and nonhomogeneity of the microstructure will lead to the decrease of threshold voltage, i.e., the grain size and thehomogeneity of the material will be important factors and directly aect the characteristic of the varistor. The sintering charac-teristic and the inuence of Bi2O3 content on the threshold voltage are also discussed..
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NMR Study of Magnetic Properties of Eu1−xSrxMnO3 (0 ≤ x ≤ 0.5)
Kenji Shimizu,Masanori Yamaguchi,Shujuan Yuan,Shixun Cao 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
The perovskite manganite EuMnO3 is known to be a compound with a narrow eg-band width due to small ionic radius of Eu3+ compared to La3+. The Eu1−xSrxMnO3 compounds show complex magnetic properties, depending on the Sr concentration x. We have carried out 55Mn spin-echo nuclear magnetic resonance (NMR) measurements on polycrystalline Eu1−xSrxMnO3 (0 ≤ x≤ 0.5) compounds at 4.2 or 1.4 K in order to clarify the microscopic local magnetic state of the Mn ions. NMR spectra have been observed in the frequency range from 250 MHz to 400 MHz. For the A-type antiferromagnetic EuMnO3, the resonance frequency is about 260 MHz, which is much lower than that observed for Mn3+ in La1−xSrxMnO3. For 0.1 ≤ x ≤ 0.4, the resonance lines corresponding to Mn4+ and Mn3+ have been observed at about 315 MHz and 390 MHz, respectively. Furthermore, the spectra originating from Mn2+ have been observed around 590 MHz for 0.1 ≤ x ≤ 0.4. For Eu0.5Sr0.5MnO3, the NMR spectrum spreads widely with several distinct peaks in the frequency range from 250 MHz to 410 MHz, which shows that the compound is in an inhomogeneous state due to competition between the antiferromagnetic and the ferromagnetic states.
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Magnetic alignment of MnBi crystals and magnetic properties of MnBi-Bi composites
Yongsheng Liu,Jincang Zhang,Zhongming Ren,Shixun Cao,Xiaoyong Zhang,Guangqiang Jia,Kang Deng,Xi Li,Junxi Zhang 한국물리학회 2007 Current Applied Physics Vol.7 No.5
Below Curie temperatureTC, MnBi crystals are aligned alongc-axis in a Bi matrix under a fabrication eldHfof 0.5 T. AboveTC,this alignment is also accomplished by quenching under a highHfof 10 T. Such a method has a prominent feature that MnBi crystalsgrow preferentially and congregate along theHfdirection. Magnetic testing shows a pronounced anisotropy in magnetization in direc-tions normal and parallel toHf, resulting from the alignment. In the case of the alignment belowTC,Hfincreases the transition temper-ature of spin-reorientation and the change in magnetization.
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Frequency and magnetic properties in the range of 10 kHz to 100 MHz for nanocrystal Fe -Co alloy
Yongsheng Liu,Jincang Zhang,Liming Yu,Guangqiang Jia,Yufeng Zhang,Xinyan Wang,Shixun Cao 한국물리학회 2004 Current Applied Physics Vol.4 No.5
Fe-based soft magnetic alloy with Co-doping was fabricated by high-energy milling. The X-ray diraction (XRD) results exhibita single phased structure,which could be regarded as BCC-like FeCo solid solution,was formed. Moreover,it has also been demonstrated that a nanocrystalline FeCo alloy was obtained and the evaluated grain sizes were about 712 nm. The frequency dependence of the initial permeability and magnetic losses,as well as DC-magnetization measurements,was systematically studiedthen. The results show that thefn (fn is the frequency when the curve of the No.n sample has a minimum value) shifts to the higherfrequency with the increasing Co content in the range of 10 kHz to 100 MHz,while the magnetic losses of the samples decrease withthe increasing Co content at the high frequency (800 kHz to 20 MHz). The Co-doping increases the cut-o frequencies of thesamples and makes the initial permeability to keep a constant value in a wider frequency range. The corresponding peak value of theinitial permeability as function of Co-doping concentration turns to the region of low Co concentration. For the long milling time,the loss apparently decreases beyond 1 MHz.
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Influence of FeSe doping on superconducting properties of MgB2 by hybrid microwave method
Cheng Cheng,Zhenjie Feng,Qing Li,Xu Wang,Chuan Yu,Hao Chu,Ya Yang,Changqin Liu,Yiming Cao,Zhe Li,Jingzhe Chen,Chao Jing,Shixun Cao,Jincang Zhang 한국물리학회 2017 Current Applied Physics Vol.17 No.11
The effect of FeSe doping on the physical properties of MgB2 is studied. Bulk samples of the FeSe doped MgB2 with weight ratio x ðFeSe : MgB2Þ ¼ 0%; 3%; 7% and 10% were prepared by hybrid microwave method. It is proved that FeSe is not stable together with MgB2. Fe2þ enters into MgB2 lattice, some Mg2þ and Se2『 are combined into the new impurity compound MgSe. The superconducting transition temperature (Tc) slightly decreased with increasing doping content of FeSe from R-T and M-T curves, which results from the substitution of Mg2þ by Fe2þ in the MgB2 lattice. The Jc increase slightly with the FeSe doping content increasing from 3 wt % to 10 wt %, which results from the increasing MgSe impurity pinning centers.
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K-doping effect of the superconductivity in K2xFeTe1-xSx (0.07 ≤ x ≤ 0.3)
Cheng Cheng,Zhenjie Feng,Qing Li,Tao Li,Qiang Hou,Fei Chen,Zhongmin Ou,Jun-Yi Ge,Shixun Cao,Jincang Zhang 한국물리학회 2019 Current Applied Physics Vol.19 No.4
Bulk samples of K doping K2xFeTe1-xSx with x=0.07, 0.1, 0.2, 0.3 are successfully prepared by using easy-to-use stable compound K2S as the reactant. The lattice constant calculated from X-ray diffraction patterns indicate that K ions enter the Fe-Te-S layers. K doping is beneficial enhance the superconductivity transition temperature from the R-T curves. The apparent diamagnetic signal is observed in M-T curves when the content of K is smaller than 0.1. However, differential curves (dM/dT) in K-rich samples appear sharp slope mutations, which means that the Meissner effect signal is covered by the increased excess ferromagnetic ions. The number of excess Fe magnetic ions is proportional to K content, which may play an important role in determining the superconductivity.
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