We investigate the thermal stability and kinetics of Cu65Hf35 bulk metallic glass （BMG）. Cu65Hf35 glassy rods in diameter up to 2 mm are prepared by a conventional copper mould suction casting. Kinetics of glass tra...We investigate the thermal stability and kinetics of Cu65Hf35 bulk metallic glass （BMG）. Cu65Hf35 glassy rods in diameter up to 2 mm are prepared by a conventional copper mould suction casting. Kinetics of glass transition and crystallizations are investigated and the ideal glass transition temperature of the alloy is obtained. It is found that the dependence of crystallization temperature of the BMG on the heating rates follows the Vogel-Fhlcher- Tammann （VFT） non-linear relationship rather than the Kissinger and Lasocka linear fittings. The long-term thermal stability of the BMG is investigated by means of continuous crystallization diagrams obtained from the extension of VFT analysis. It is suggested that ideal glass transition and crystallization temperatures can also be regarded as the long-term stability criteria of the BMG.展开更多
We perform the high-pressure energy dispersive x-ray diffraction experiments of nickel nanoparticle chain using a synchrotron source under quasi-hydrostatic compression up to 44.7GPa. There is no phase transition over...We perform the high-pressure energy dispersive x-ray diffraction experiments of nickel nanoparticle chain using a synchrotron source under quasi-hydrostatic compression up to 44.7GPa. There is no phase transition over the pressure range. The bulk modulus Ko, the first pressure derivative of bulk modulus K＇0 and the volume Vo are calculated from the pressure-volume data using the Birch-Murnaghan equation of state. A decrease of compressibility is observed, in agreement with the Hall-Perch effect.展开更多
Electronic structure of SmCo7-xHfx compound is calculated by using the multi-scattering Xα method. It is shown that a few of electrons can transfer to the Sm 5d orbital due to orbital hybridization between Sm and Co ...Electronic structure of SmCo7-xHfx compound is calculated by using the multi-scattering Xα method. It is shown that a few of electrons can transfer to the Sm 5d orbital due to orbital hybridization between Sm and Co atoms. The 3d-5d coupling is stronger, which is the main reason to result in the long-range ferromagnetic order between Sm and Co atoms in SmCo7-xHfx. According to the Stoner criterion, the result of spin-unpolarized calculation for the Sm5Co32Hf2 duster could lead to a better understanding of why the ferromagnetic SmCo7-xHfx is a stable phase. For the Sm5Co32Hf2 duster the Fermi level is situated at the overall maximum of the density of states. Moreover the duster wavefunctions at EF are antibonding and hence highly localized in real space, which would lead to a large value for the duster Stoner integral. Thus a rationalization for the magnetic stability of SmCo7-xHfx has been obtained.展开更多
We investigate the effect of N2 addition during sputtering on the microstructure and magnetic properties of FePt-Al2O3 thin films. The texture of FePt phase in FePt-Al2O3 thin films changes from （111） to a more rand...We investigate the effect of N2 addition during sputtering on the microstructure and magnetic properties of FePt-Al2O3 thin films. The texture of FePt phase in FePt-Al2O3 thin films changes from （111） to a more random orientation by N2 addition during sputtering. The ordering temperature of FePt phase reduces about 100℃ with appropriate N2 partial pressure. A larger coercivity of 6.0 × 10^5 Aim is obtained with N2 partial pressure about 15%. Structural analysis reveals that a small quantity of Fe3N phase forms during sputtering and the release of N atoms during the post annealing induces a large number of vacancies in the films, which benefits to the transformation of FePt phase from fcc to fct.展开更多
We perform the ab initio calculation for obtaining the density of states and magnetic properties of ZrFe2 Laves phase compound based on the method of augmented plane waves plus local orbital The results indicate that ...We perform the ab initio calculation for obtaining the density of states and magnetic properties of ZrFe2 Laves phase compound based on the method of augmented plane waves plus local orbital The results indicate that the ferromagnetic state is more stable than the paramagnetic one, but with a slightly larger volume. The 3d - 4d exchange interactions between Fe and Zr electrons lead to the antiparallel coupling for Fe 3d and Zr 4d states, which is responsible for the ferrimagnetic ordering of the compound. The resulting magnetic moment of about 1.98μB for Fe is spatially localized near the Fe site, while around Zr a small but extended negative spin states causes a moment of about -0.44 μB. Moreover, the resulting magnetic moments with the generalized gradient approximation are more consistent with experimental values than that of the local-spin density approximation.展开更多
Zn1-xMnxO （x = O.Olq3.1） thin films with a Curie temperature above 300K are deposited on Al2O3 （0001） substrates by pulsed laser deposition. X-ray diffraction （XRD）, ultraviolet （UV）-visible transmission and R...Zn1-xMnxO （x = O.Olq3.1） thin films with a Curie temperature above 300K are deposited on Al2O3 （0001） substrates by pulsed laser deposition. X-ray diffraction （XRD）, ultraviolet （UV）-visible transmission and Raman spectroscopy are employed to characterize the microstructural properties of these films. Room temperature ferromagnetism is observed by superconducting quantum interference device （SQUID）. The results indicate that Mn doping introduces the incorporation of Mn^2＋ ions into the ZnO host matrix and the insertion of Mn^2＋ ions increases the lattice defects, which is correlated with the ferromagnetism of the obtained films. The doping concentration is also proven to be a crucial factor for obtaining highly ferromagnetic Zn1-xMnxO films.展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 50471099 and 50671058, and the Natural Science Foundation of Shanghai Municipal Science and Technology Commission under Grant No 06ZR14036.
文摘We investigate the thermal stability and kinetics of Cu65Hf35 bulk metallic glass （BMG）. Cu65Hf35 glassy rods in diameter up to 2 mm are prepared by a conventional copper mould suction casting. Kinetics of glass transition and crystallizations are investigated and the ideal glass transition temperature of the alloy is obtained. It is found that the dependence of crystallization temperature of the BMG on the heating rates follows the Vogel-Fhlcher- Tammann （VFT） non-linear relationship rather than the Kissinger and Lasocka linear fittings. The long-term thermal stability of the BMG is investigated by means of continuous crystallization diagrams obtained from the extension of VFT analysis. It is suggested that ideal glass transition and crystallization temperatures can also be regarded as the long-term stability criteria of the BMG.
文摘We perform the high-pressure energy dispersive x-ray diffraction experiments of nickel nanoparticle chain using a synchrotron source under quasi-hydrostatic compression up to 44.7GPa. There is no phase transition over the pressure range. The bulk modulus Ko, the first pressure derivative of bulk modulus K＇0 and the volume Vo are calculated from the pressure-volume data using the Birch-Murnaghan equation of state. A decrease of compressibility is observed, in agreement with the Hall-Perch effect.
基金Supported by the National High-Technology Research and Development Programme of China under Grant No 2002AA324050, and the Natural Science Foundation of Shandong Province under Grant Nos Y2002D9 and Y2004A10.
文摘Electronic structure of SmCo7-xHfx compound is calculated by using the multi-scattering Xα method. It is shown that a few of electrons can transfer to the Sm 5d orbital due to orbital hybridization between Sm and Co atoms. The 3d-5d coupling is stronger, which is the main reason to result in the long-range ferromagnetic order between Sm and Co atoms in SmCo7-xHfx. According to the Stoner criterion, the result of spin-unpolarized calculation for the Sm5Co32Hf2 duster could lead to a better understanding of why the ferromagnetic SmCo7-xHfx is a stable phase. For the Sm5Co32Hf2 duster the Fermi level is situated at the overall maximum of the density of states. Moreover the duster wavefunctions at EF are antibonding and hence highly localized in real space, which would lead to a large value for the duster Stoner integral. Thus a rationalization for the magnetic stability of SmCo7-xHfx has been obtained.
文摘We investigate the effect of N2 addition during sputtering on the microstructure and magnetic properties of FePt-Al2O3 thin films. The texture of FePt phase in FePt-Al2O3 thin films changes from （111） to a more random orientation by N2 addition during sputtering. The ordering temperature of FePt phase reduces about 100℃ with appropriate N2 partial pressure. A larger coercivity of 6.0 × 10^5 Aim is obtained with N2 partial pressure about 15%. Structural analysis reveals that a small quantity of Fe3N phase forms during sputtering and the release of N atoms during the post annealing induces a large number of vacancies in the films, which benefits to the transformation of FePt phase from fcc to fct.
基金Supported by the Natural Science Foundation of Shandong Province under Grant Nos Y2002D9 and Y2004A10, and the Doctoral Foundation of Jinan University under Grant No B0632.
文摘We perform the ab initio calculation for obtaining the density of states and magnetic properties of ZrFe2 Laves phase compound based on the method of augmented plane waves plus local orbital The results indicate that the ferromagnetic state is more stable than the paramagnetic one, but with a slightly larger volume. The 3d - 4d exchange interactions between Fe and Zr electrons lead to the antiparallel coupling for Fe 3d and Zr 4d states, which is responsible for the ferrimagnetic ordering of the compound. The resulting magnetic moment of about 1.98μB for Fe is spatially localized near the Fe site, while around Zr a small but extended negative spin states causes a moment of about -0.44 μB. Moreover, the resulting magnetic moments with the generalized gradient approximation are more consistent with experimental values than that of the local-spin density approximation.
基金Supported by the Natural Science Foundation of Hebei Province under Grant No E2006001006, and the Programme for New Century Excellent Talents at the University of the Ministry of Education of China.
文摘Zn1-xMnxO （x = O.Olq3.1） thin films with a Curie temperature above 300K are deposited on Al2O3 （0001） substrates by pulsed laser deposition. X-ray diffraction （XRD）, ultraviolet （UV）-visible transmission and Raman spectroscopy are employed to characterize the microstructural properties of these films. Room temperature ferromagnetism is observed by superconducting quantum interference device （SQUID）. The results indicate that Mn doping introduces the incorporation of Mn^2＋ ions into the ZnO host matrix and the insertion of Mn^2＋ ions increases the lattice defects, which is correlated with the ferromagnetism of the obtained films. The doping concentration is also proven to be a crucial factor for obtaining highly ferromagnetic Zn1-xMnxO films.
