刘公强
凝聚态物理
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 姓名：刘公强
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博士生导师
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凝聚态物理学
 研究兴趣：凝聚态物理
刘公强（Liu Gongqiang）1941年11月生，男。1964年7月南京大学物理系磁学专业毕业。上海交通大学物理系教授、博士生导师，国务院特殊津贴获得者。兼任上海市稀土学会理事、上海市物理学会磁学和磁性材料专业委员会主任、中国物理学会磁学和磁性材料专业委员会委员等职。长期从事凝聚态物理教学和科研工作。主要讲授固体物理、磁光物理、铁磁学和电磁学等课程。二十多年来主持研究了《光孤子通信无源器件的研制》、《Faraday 磁光效应及其温度、色散特性的微观机理研究》、《磁光波导中的静磁波传播与光衍射效应研究》、《光磁效应的研究》和《组合合成、高通量筛选技术的应用与热敏铁氧体系列材料的研制》等近三十项课题的研究工作，其中技术鉴定十六项，半数达到国际先进水平。《磁光旋转测试方法和装置》1987年获国家发明三等奖，《光隔离器》1993年获上海市科技进步二等奖，《组合合成、高通量筛选技术的应用与热敏铁氧体系列材料的研制》2003年获上海市科技进步三等奖（以上均为第一获奖者）。此外还获得“星火杯”发明奖（第一获奖者）、省部级科技奖、研究生优秀导师奖和思源优秀教师一等奖等奖励多次。著作有《磁学小实验》（上海科学技术出版社，1982年出版）、《磁光材料和磁光器件》（北京科学技术出版社，1990年出版）和《磁光学》（上海科学技术出版社，2001年5月出版）等．发表论文一百二十篇，多篇论文获奖。专利四项。

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【期刊论文】Photomagnetic effect of a magnetic impurity embedded in a nonmagnetic base
刘公强， J. H. Cai*， G. Q. Liu
PHYSICAL REVIEW B, VOLUME 64, 014409，0001，（）：
1年11月30日
The sd mixing model, in which electronphoton coupling was taken into account, was employed to study the effect of optical irradiation on the moment of a magnetic impurity embedded in a nonmagnetic base. The local magnetic moment was calculated selfconsistently by employing the Greenfunction technique. There exists notable photomagnetic effect, while the energy level configuration meets the resonantabsorption condition and the effective onsite energy of local electrons approaches the Fermi energy Ef. The change of local moment primarily originates from the transition between a dlike local state and a plike local (extended) state. The mechanism of photomagnetic effect of a magnetic impurity is that the optical irradiation breaks the original balance of electron distribution under Column interaction (Hubbard repulsion) via the change of local energylevel position and the decrease of its lifetime and hence results in the variation of local magnetic moment.

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刘公强， Si XinWen a， *， Liu GongQiang b， c
Journal of Magnetism and Magnetic Materials 223(2001)147～155，0001，（）：
1年11月30日
Under inclined magnetic field, the propagation characteristics of magnetostatic waves (MSWs) for a doublelayered waveguided structure are theoretically studied by using surface permeability method. A new concept called & mode interlamination coupling' is proposed by analysis of mode spectrum, which develops a generalized understanding of the MSWs propagating in a layered structure. A similar treatment can be applied to the situation of multilayered structure under inclined field. In addition, the dispersion relation and delay characteristics of coupled mode in two different YIG films are studied by numerical analogue at inclination angle from 5 to 20
Magnetostatic wave， Inclined magnetic field， Waveguided film， Dispersion relation， Mode lamination coupling

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刘公强， Wu BaoJian a)， Liu GongQiang
J. Appl. Phys. 1999, 86(8):4365～4368，0001，（）：
1年11月30日
The noncollinear interaction between guided optical waves and magnetostatic waves under inclined bias magnetic field is studied in detail. The diffraction efficiency (DE) and the modeconversion efficiency (MCE) of guided optical waves with magnetostatic forward volume waves in the bismuthdoped yttriumirongarnet (Bidoped YIG) waveguide are calculated numerically. The calculation results indicate that the DE and the MCE are different in physical conception and the DE is not equal to the MCE in magnitude under inclined bias magnetic field. The DE may be greatly increased by using an appropriately inclined bias magnetic field, which has been experimentally confirmed in a pure YIG waveguide. By using an inclined bias magnetic field and the Bidoped YIG waveguide, under the phasematching conditions, the maximum DE can come up to 79.5% or more.

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【期刊论文】Calculation of the magnetic susceptibility and the Verdet constant in neodymium trifluoride
刘公强， Gongqiang Liu， Bin Yuan and Ninggao Zhang， Xiaoyan Gong
J. Appl. Phys. 1995, 78(6):4054～4059，0001，（）：
1年11月30日
This paper first considers the effects of multielectron interaction, LS interaction and the weak crystalfield on the 4f3 ground state of Nd3+ ion in the paramagnetic medium NdF3; then, further takes account of the splitting of the crystalfield ground levels caused by both the effective superexchange field Hv and the applied field He, and calculates quantitatively the temperature dependence of the magnetic susceptibility x in NdF3. For the splitting of 4f25d excited state of Nd3+ ion in NdFs, the paper investigates the effect of the strong crystalfield on the 5d electrons. Using the model of threelevel transition, the specific Faraday rotation θF, the Verdet constant V, and their temperature dependence, which originate from the electronic transitions between the electron configurations 4f3 and 4f25d, are calculated quantitatively. The theoretical calculations show that the superexchange interaction between Nd3+ ions has an important effect on the magnetooptical properties in NdF3, and both V1 and x1 are linearly dependent on T in the temperature range 70 K<T<300 K. The theory is in good agreement with the experimental results.

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刘公强， Liu Gongqiang†‡， Zhang Xing‡， Zhang Ningao‡ and Yuan Bin‡
J. Phys: Condens. Malter 6(1994)453460，0001，（）：
1年11月30日
This paper first considers the effects of LS interaction and the crystal field on both the 4Fground state and the 5d excited state of Pr 3+ ions in the paramagnetic material PrF3, and further takes account of the splitting of the crystalfield ground levels caused by the effective superexchange field H Y and the applied field He, and then, using the model of double tramition with the splitting of the ground stale, cabdates quantitatively the magnetic susceptibility x, specific Faraday rotation θF. Verdet constant V. and their temperature dependence in PrF3. The theoretical calculations show that the magnetooptical effect and its temperature dependence in PrF3 are closely related to the superexchange interaction between Pr3+ ions. V1 and X1 are linearly dependent of T in the temperature range of [10K≤T≤300K and independent of T in the lowtemperature regime. The theory is in agreement with the experimental results.

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【期刊论文】Quantitative analyses of magnetic and magnetooptical properties in cerium trifluoride
刘公强， Liu Gongqiang， Zhang Wenkang and Zhang Xing
PHYSICAL REVIEW B, 1993 48(21):16091～16094，0001，（）：
1年11月30日
We first consider the effects of the crystal field on both the 4f ground state and the 5d excited state of a Ce3+ ion in the paramagnetic medium CeF3, and further take account of the splitting of the crystalfield groundstate levels caused by the effective superexchange field Hv and the applied field He; then, with a model of a double transition that includes groundstate splitting, we calculate quantitatively the specific Faraday rotation θF, the Verdet constant V, the magnetic susceptibility X, and their temperature dependences in CeF3. Theoretical calculations show that the magnetooptical effect and its temperature dependence in CeF3 are closely related to the superexchange interaction between Ce3+ ions. V1 is linearly dependent on T and V/X=18353(1+63.01/T) in the temperature range 60<T≤300K. The theory is in good agreement with the experimental results.

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【期刊论文】Fourlevel transition model and the Faraday effect in ferrimagnetic media
刘公强， Liu Gongqiang， Zuo Wende
PHYSICAL REVIEW B, 1991 44(2):699～704，0001，（）：
1年11月30日
In ferrimagnetic media, besides originating from the splitting of the excited state resulting from the spinorbit interaction, magnetooptical effects also arise from the splitting of the ground state caused by the superexchange interaction and applied field. A theoretical calculation according to this view shows that the Faraday rotation 0 depends linearly on sublattice magnetization Mi (i=1,2,..., l) in both the lowtemperature and hightemperature regimes for the medium with high Curie temperature, while in the normaltemperature regime, 0 depends nonlinearly on each Mi and T. The theory is in good agreement with experimental results.

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【期刊论文】Faraday effect and the effective field theory in solid materials
刘公强， Liu Gongqiang， Yu Zhiqiang and Le Zhiqiang
Journal of Magnetism and Magnetic Materials 96(1991)155～161，0001，（）：
1年11月30日
Having used the classical electromagnetic field theory and combined it with the effectivefield conception, in this paper we show that: 1) The real part θ of Faraday rotation φ in any kind of the magnetooptical (MO) material can be expressed in the fundamental form of θ=VLHi. 2) The differences in the MO properties of the different kinds of the MO media mainly result from both the characteristics and the size of their effective field Hi and especially, the different temperature properties in various media are discussed. 3) The relationship between the real part θ and the imaginary part ψ of φ can be described by the effective extinction coefficient η*. 4) The other MO properties are predicted. It is proved that the effective field Hv, which is concerned in both the spinorbital interaction and the exchange interaction (or the indirect exchange interaction) in media, can be expressed in the form of Hv=vM (or E1=1viMi). Some theoretical results are verified by experiments.

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【期刊论文】The fourlevel transition model and the Faraday effect in ferromagnetic media
刘公强， Gongqiang Liu， Wende Zuo and Zhiqiang Le
J. Appl. Phys. 1991, 63(3):1591～1595 ，0001，（）：
1年11月30日
In ferromagnetic media, besides originating from the splitting of the excited state resulting from the spinorbit interaction, magnetooptical effects also arise from the splitting of the ground state caused by both the exchange interaction and the applied field. In view of the standpoint mentioned above, it is shown by calculation that the Faraday rotation 0 depends linearly on magnetization M in both the regions of T<T, (Curie temperature) and of high temperature for the medium with high T c, but nonlinearly on M and Tin the usual temperature region between the above two regions.

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【期刊论文】Quantum theory of the Faraday magnetooptical effect in paramagnetic media
刘公强， Liu Gongqiang， Huang Yanping， and Yu Zhiqiang
PHYSICAL REVIEW B, 1990 41(1):749～753，0001，（）：
1年11月30日
In some paramagnetic media, the effective field Hi, which includes an effective exchange field and an applied field, can cause a splitting of the ground level. In the temperature region T>Tc (Tc is the Curie temperature), there are certain probability distributions of electrons on two energy levels due to groundstate splitting. This induces the ground level for a double transition. It is shown that there are several temperature behaviors for the magnetooptical Faraday effect in paramagnetic media. If the applied field is not too large, the ratio of the Verdet constant to the magnetic susceptibility is V/x=A (1+BT) in some media, or V/x=A (1+B/T) in other media. It is also indicated that both the real part θ' and imaginary part θ" of the Faraday rotation are proportional to the effective field Hl, and show similar temperature behaviors beyond the region of optical absorption.

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