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Soft magnetic properties of (Ni_(50)Fe_(50)) SiO_2 granular thin films for high frequency application

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Rare Metals 2006年第Z1期25卷 650-654页

作者： YANG Xiaolin GE Shihui RUAN Chengli College of Physics and Electronic Science University of Electronic Science and Technology of China Chengdu 610054 China Key Laboratory for Magnetism and Magnetic Materials of Ministry of EducationLanzhou University Lanzhou 730000 China College of Physics and Electronic Science University of Electronic Science and Technology of China Chengdu 610054 China

A series of (Ni50Fe50)x(SiO2)(1-x) films with different volume fraction x was fabricated by magnetron co-sputtering technique. The microstructure, magnetic and electrical properties were investigated systematically by using X-ray diffraction, transmission electronic microscope, vibrating sample magnetometer and the traditional four point measurement method of resistivity. The results show that the samples consist of nano-scaled Ni50Fe50 metallic particles with fcc structure uniformly embedded in amorphous insulating SiO2 matrix, and the particle size decreases with the decrease of x. The rapid change of coercivity with x is observed, and a minimum value 160 A·m-1 of Hc was obtained for the sample of x=0.83 with film thickness of 180 nm, which can be contributed to the exchange coupling between nano-scaled Ni50Fe50 particles. At the frequency lower than 1 GHz, the real part μ′ of complex permeability keeps about 110 and the image part μ″ is less than 15. Besides, this film exhibits high resistivity ρ=263 μΩ·cm, high saturation magnetization 4πMs=1.25 T, high in-plane magnetic anisotropy field Hk=6.37 kA·m-1, and the ferromagnetic resonance (FMR) frequency is estimated to be 2.8 GHz. Therefore, this film can be used in high frequency devices operating over 2 GHz.

关键词： thin films nanostructure magnetic properties

A study of magnetostriction, spin reorientation, and Mssbauer spectra of Tb_(0.3)Dy_(0.6)Pr_(0.1)(Fe_(1-x)Al_x)1.95 alloys with substitution of Fe by Al

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Science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 449-453页

作者： ZHENG XiaoPing1,3, ZHANG PeiFeng1,2, LI FaShen2 & HAO Yuan2 1 Institute of Electronic Information Science and Technology, lanzhou City university, lanzhou 730070, china 2 key laboratory for magnetism and magnetic materials, ministry of education, lanzhou university, lanzhou 730000, china 3 State key laboratory of Advanced Non-Ferrous materials, Gansu Province, lanzhou university of Technology, lanzhou 730050, china 1. Institute of Electronic Information Science and Technology Lanzhou City University Lanzhou 730070 China3. State Key Laboratory of Advanced Non-Ferrous Materials Gansu Province Lanzhou University of Technology Lanzhou 730050 China2. Key Laboratory for Magnetism and Magnetic Materials Ministry of Education Lanzhou University Lanzhou 730000 China

The effects of Al substitution for Fe on the structure, magnetics, magnetostriction, anisotropy and spin reorientation of a series of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys (x=0.05, 0.1, 0.15, 0.2, 0.25, 0.3) at room temperature have been investigated. The alloys of Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 substantially retain MgCu2-type C-15 cubic Laves phase structure when x2. The mixed phases appear with x = 0.2, and cubic Laves phase decreases with increasing x. The magnetostriction of the Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95 alloys decreases drastically with increasing x and the giant magnetostrictive effect disappears for x > 0.15. Fortunately, a small amount of Al substitution is beneficial to a decrease in the magnetocrystalline anisotropy. The spin reorientation temperature decreases with increasing x. The analysis of the Mssbauer spectra indicates that the easy magnetization direction in the {110} plane deviates slightly from the main axis of symmetry with the increase of Al concentration x, namely, spin reorientation, resulting in the change of macroscopical magnetic properties and magnetostriction. The hyperfine field decreases, but the isomer shifts increases with Al concentration increasing and the quadruple splitting QS shows a weak concentration dependence.

关键词： cubic laves phase magnetostriction spin reorientation Mssbauer

magnetic properties and tunneling magnetoresistance in FeCo-SiO_2 granular films

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Chinese Science Bulletin 2001年第9期46卷 734-737页

作者： XI Li, ZHANG Zongzhi, CHI Junhong, LI Chengxian & GE Shihuikey laboratory for magnetism and magnetic materials of the ministry of education, lanzhou university, lanzhou 730000, china key laboratory for magnetism and magnetic materials of the ministry of education Lanzhou University Lanzhou China

Fefv(SiO2)1-fv granular films were fabricated by rf sputtering (fv represents the Fe volume fraction). The mi-crostructure, magnetic properties as well as the tunneling magnetoresistance effect (TMR) were systematically studied. It was found that the maximum TMR ratio is about -3.3% at fv = 0.33. Under the same condition, a series of (Fe100-x Cox)0.33(SiO2)0.67 were prepared. TMR value reaches -4.5% at x=53, while the microstructure of the film still keeps as that of Fe0.33(SiO2)0.67. The higher TMR ratio is contributed to the elevating of the spin polarization of particles. This is consistent with Inoue’s theory.

关键词： tunneling magnetoresistance granular films.

MULTISCALE MECHANICAL BEHAVIORS IN DISCRETE materials: A REVIEW

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Acta Mechanica Solida Sinica 2010年第6期23卷 579-591页

作者： Xiaojing Zheng Dengming Wang (key laboratory of Mechanics on Western Disaster and Environment,the ministry of education of china,lanzhou university,lanzhou 730000,china) key laboratory of Mechanics on Western Disaster and Environment the Ministry of Education of China Lanzhou University Lanzhou China

The discrete material, which belongs to the category of soft materials, is one of the most prevalent forms of matter in nature and engineering fields. These materials often exhibit abundant and complex mechanical properties which are still far from being perfectly understood. From the view of multi-scale framework concentrated on the ＇bridge＇ role in the macro-micro relation, this review mainly introduces some theoretical investigations of mechanical behaviors in discrete materials, including the continuum constitutive model based on the macroscopic phenomenological approach and coupled micro-macro approach, the statistical analysis of some microscopic physical quantities involved contacted forces between particles and its transmission within the whole system, and the statistical analysis for some microscopic processes in aeolian landform systems involving the grain-bed impact, the transportation and sedimentation of wind-blown sand flux, et al. Finally, some further worthwhile challenges in these fields are suggested.

关键词： discrete material multiple space and time scales trans-scales correlation sanddune statistical analysis

Dating and genesis of the upper Weihe River terraces in Longxi basin,china

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Progress in Natural Science:materials International 2007年第11期17卷 1334-1340页

作者： Pan Baotian, Liu Xiaofeng, Gao Hongshan, Wang Yong and Li Jijun(key laboratory of Western china’s Environmental System, ministry of education, lanzhou university, lanzhou 730000, china) key laboratory of Western china's Environmental System Lanzhou University Lanzhou 730000 China

Seven terraces along the Weihe River in Longxi basin have been investigated. These terraces all consist of archetypal duality in structure, namely the floodplain deposits and the layer of gravels overlaid by varying thickness of the loess. By resorting to various dating approaches such as palaeomagnetic, optically stimulated luminescenece (OSL), 14C and loess-paleosol sequence, we provide preliminary timing of these seven terraces along upper Weihe River. Analysis on sedimentation characteristics and dating of these terraces showed that seven terraces may be jointly generated by tectonic uplifts and climatic changes. Tectonic uplifts may accommodate initial river incision, and climatic change may be responsible for processes of subsequent channel widening and aggradation. Aggradation normally occurs during glacial periods, in contrast to down-cuttings during transitions from glacial to interglacial period. Moreover, on the basis of the timings and heights of these terraces, we infer that the long-term rate of river incision was determined to be 0.2 m/kyr during the last 870 kyr, which differs from other river incision rates. This discrepancy may reflect spatio-temporal differentiation of tectonic activities in the Qinling orogenic belt during the Pleistocene.

关键词： loess stratigraphy river terraces climate change Upper Weihe River

magnetic characteristics of dustfall in urban area of north china and its environmental significance

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Science china Earth Sciences 2007年第11期50卷 1724-1732页

作者： XIA DunSheng1,2, YANG LiPing2, MA JianYing1, YU Ye1, WANG Guan2 & CHEN FaHu2 1 key laboratory of Desert and Desertification, Institute of Cold and Arid Regions Environmental and Engineering, Chinese Academy of Sciences, lanzhou 730000, china 2 CAEP, key laboratory of West china’s Environmental System (ministry of education), lanzhou university, lanzhou 730000, china key laboratory of Desert and Desertification Institute of Cold and Arid Regions Environmental and Engineering Chinese Academy of Sciences Lanzhou China CAEP Key Laboratory of West China’s Environmental System (Ministry of Education) Lanzhou University Lanzhou China

Urban particulate pollutants not only affect urban air quality but also directly threaten public health. lanzhou has been one of the most seriously polluted cities in the world due to its special geophysical location and weather conditions, which makes it an ideal place for urban particulate pollution study. In this study a set of environmental magnetic parameters (χ_(1f),χ_(fd)%, χ_(ARM), SIRM, HIRM, SOFT and back field IRM) were measured and analyzed for the dustfall samples collected monthly during 1997.4—2000.5 and 2004.11—2005.10 at lanzhou university campus (KLD and CCS) and at a clear site of Gaolanxian (GLX). Results demonstrate that the main magnetic minerals in the dustfall are magnetite, with some maghaemite and haematite. Cross plots of M_(rs)/M_s vs. B_(cr)/B_c and χ_(fd)% vs. χ_(ARM)/SIRM indicate that the main magnetic grain sizes are pseudo-single-domain (PSD). The high concentration of magnetic minerals in the dustfall indicates that lanzhou is seriously polluted. The main pollution sources are anthropogenic activities and nature dust, with the former posing a great threat during the whole year, which is different from the general view that the natural dust is the main contributor in summer. With great efforts of the government and local authority in the past decades, the air quality in lanzhou has been improved in winter, but it is not so obvious in summer. This study also reveals that as a simple, rapid and accurate technology, environmental magnetism could be a valuable tool for urban pollution study.

关键词： environmental magnetism,dustfall,air pollution,lanzhou

Discovery of a 1.0 Ma Yellow River terrace and redating of the fourth Yellow River terrace in lanzhou area

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Progress in Natural Science:materials International 2007年第2期17卷 197-205页

作者： PAN Baotian , SU Huai, HU Chunsheng, HU Xiaofei, ZHOU Tian and LI Jijun (key laboratory of Western china’s Environmental Systems, ministry of education, and Department of Geography, lanzhou university, lanzhou 730000, china) key laboratory of Western china's Environmental System MOE Department of Geography Lanzhou University Lanzhou 730000 China

Based on the aeolian loess sequence-stratigraphic division and paleomagnetic datings on terraces, we found that an undiscovered terrace with the age of 1.0 Ma BP lies between the Dunwashan terrace and Wuyishan terrace. This terrace recorded an intensive Yellow River incision event during that period. Results of paleomagnetic dating and optically stimulated luminescence (OSL) dating of the Wuyishan loess section and Zaoshugou loess section on the fourth Yellow River terrace (T4) show that the age of the fourth Yellow River terrace in lanzhou area is 0.86 Ma BP rather than the previously believed 0. 6 Ma BP. This result answers a long-term question in the ge-omorphology community of whether there exists a 0. 8 Ma terrace in lanzhou area. The discovery of the 1. 0 Ma Yellow River terrace and redating of the age of 0.6 Ma terrace in lanzhou area provide new insights into further research on the evolution of Yellow River.

关键词： lanzhou area Yellow River terrace dating.

Terrace dating as an archive of the run-through of the Sanmen Gorges

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Progress in Natural Science:materials International 2005年第12期15卷 1096-1103页

作者： PAN Baotian,WANG Junping,GAO Hongshan,CHEN Yingying,LI Jijun and LIU Xiaofeng key laboratory of Western china’s Environmental Systems,ministry of education,and Department of Geography,lanzhou university,lanzhou 730000,china key laboratory of Western china's Environmental Systems of ministry of education Department of Geography Lanzhou University Lanzhou 730000 China

Analysis of morphological properties in the Sanmen Gorges region of the Yellow River shows that four river terraces have been developed at the entrance to the ***,thick aeolian loess-paleosol sequence was deposited on the terraces,which makes it easy to date the *** dating of paleomagnetic,loess-paleosol sequence matching and thermoluminescence show that terraces T2,T3 and T4 were formed 0.129 Ma,0.625 Ma and 0.865 Ma ago,*** formation of these terraces in this region indicates that the Yellow River has experienced four intensive downcutting events during the last 0.9 *** Yellow River cut through the Sanmen Gorges and inpoured into the East china Sea no later than 0.865 Ma.

关键词： river terrace paleomagnetic dating Yellow River loess

Effect of TRT process on GFA,mechanical properties and microstructure of Zr-based bulk metallic glass

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Progress in Natural Science:materials International 2011年第1期21卷 53-58页

作者： Guang-qiao LIU~1,Sheng-zhong KOU~(1,2),Chun-yan LI~1,Yan-chun ZHAO~1,Hong-li SUO~2 1.State key laboratory of Gansu Advanced Non-ferrous Metal materials, lanzhou university of Technology,lanzhou 730050,china 2.The key laboratory of Advanced Functional materials(ministry of education), Beijing university of Technology,Beijing 100022,china State key laboratory of Gansu Advanced Non-ferrous Metal materials Lanzhou University of Technology Lanzhou 730050 China The key laboratory of Advanced Functional materials (ministry of education) Beijing University of Technology Beijing 100022 China

Series of rod samples of Zr55Al10Ni5Cu30 alloy were prepared by magnetic suspend melting and copper mold suction casting *** effect of thermal rate treatment（TRT） process on glass forming ability（GFA）,mechanical properties and microstructure of Zr-based bulk metallic glass were *** shows that GAF,mechanical properties and microstructure of as-cast Zr55Al10Ni5Cu30 BMGs alloy to a large extent is related to TRT *** and thermal stability of as-cast Zr55Al10Ni5Cu30 alloy increase when overheating temperature *** liquid region△Txand parameterγincrease from 73 K to 89 K,from 0.413 to 0.417,respectively,when casting voltage increases from 7 kV to 10 *** a threshold overheating temperature is found for the fully amorphous structure,below which it may have an intersection with the crystallization *** is found that the compressive strength increases and the compressive plasticity slightly decreases when overheating temperature ***,the compressive strength and the compressive plasticity simultaneously increase to 1.91 MPa and 2%when casting voltage increases to 10 kV.

关键词： bulk metallic glass glass forming ability(GFA) mechanical properties thermal rate treatment(TRT) process microstructure