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spin Dependent Hopping in Ti Doped La_(0.67)Ca_(0.33)MnO_3

Journal of Rare Earths 2004年第6期22卷 803-807页

作者：黄宝歆刘宜华张汝贞原晓波王成建梅良模 Department of Physics State Key Laboratory of Crystal Materials Shandong University Department of Physics Weifang University Weifang 261061China

A systematic investigation of the magnetic and transport properties of Ti doped La_(0.67)Ca_(0.33)MnO_3 was reported. The Ti substitution for Mn ions results in a reduction in ferromagnetism and conductivity. The metal-insulator transition temperature is close to Curie temperature which decreases from 274 to 82 K as x increases from 0 to 0.17. The most important effect of Ti doping is to introduce spin clusters in the samples due to the distortion of local lattice and the inhomogeneous magnetic structure induced primarily by the random distribution of Mn ions. A maximum magnetoresistance ratio as large as 90% in 1 T at 122 K was obtained for the sample with x=0.055, which is four times larger than that obtained for LCMO sample at 272 K. There is a remarkable field-history dependent MR in the cooling process for the doped samples while such phenomenon disappears in the warming run. The resistivity follows well the variable range hopping behavior in paramagnetic state. Both the size effect and spin dependent hopping of carriers between the spin clusters should be considered in this system.

关键词： ceramic materials colossal magnetoresistance spin cluster rare earths

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Physical Realization of Quantum C-Not Gate

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Chinese Physics Letters 2008年第3期25卷 813-816页

作者：霍建立王顺金陶军 Center of Theoretical Physics School of Physics and Technology Sichuan University Chengdu 610064

We investigate a Heisenberg spin cluster with two particles controlled by a time-dependent magnetic field. The system is controlled by tuning the amplitude, frequency, and interaction time of the three-step time-dependent magnetic field. Then we solve the time-dependent Schrodinger equation of the two-particle system, and obtain the time evolution operator. By the three-timestep interaction, the wavefunction evolves from the initial state to the final state, and the total evolution operator can be expressed as a product of the three evolution operators. By adjusting the physical parameters, the key two-qubit logic gate, the C-Not gate, can be realized physically.

关键词： spin cluster COMPUTATION QUBITS LOGIC

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Irreversible Colossal Magnetoresistance in La_(0.58)Dy_(0.09)Ca_(0.33)MnO_3

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Journal of Materials Science & Technology 2003年第6期19卷 622-624页

作者： Baoxin HUANG, Yihua LIU, Ruzhen ZHANG, Youyong DAI, Chengjian WANG, Xiaobo YUAN and Liangmo MEIDepartment of Physics and State Key Laboratory of Crystal Materials, Shandong University, Ji’nan 250100, China Lab. of Crystal Mat. Dept. of Phys. Shandong Univ. Ji'nan 250100 China

The representative sample La0.58Dy0.09Ca0.33MnO3 of Dy doped La0.67Ca0.33MnO3 rare-earth manganites was investigated. The most important effect of Dy doping is to introduce the magnetoimpurity and form the spin clusters which induce dramatically large CMR in La0.58Dy0.09Ca0.33MnO3. The fitting results of field-induced resistivity decrease to the Brillouin function indicate that the CMR is caused by the spin dependent hopping between spin clusters. It is the magnetic field that reduces the size of spin clusters and induces a field-induced irreversible CMR behaviour.

关键词： spin cluster Magnetoimpurity Colossal magnetoresistance

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Improvement on Electrical Properties and Magnetoresistance Induced by Pd or Ag Addition in Lao.67（Ca0.65Ba0.35）0.33MnO3 Manganites

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Chinese Journal of Chemical Physics 2013年第4期26卷 431-438,J0002页

作者：原晓波任俊峰山东师范大学物理与电子科学学院济南250014

Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd and Ag addition induce a decrease in resistivity and an increase in temperature at which the resistivity reaches its maximum. This is mainly due to the improvement of grain boundaries caused by the segregation of good conductive metal grains on the grain boundaries/surfaces. In addition, both Pd and Ag addition induce a large enhancement of room temperature magnetoresistance （RTMR）. Note that 27% molar ratio of Ag addition induces a large RTMR of about 70%, about ten times larger than pure LCBMO, whereas 27% molar ratio Pd addition brings a much larger RTMR of about 170%. The large enhancements of MR can be attributed to the decrease in resistivity of the samples caused by the good conductive metal. On the other hand, the polarization of Pd atoms near the Mn ions on the grain surfaces/boundaries plays a very im-portant role in the increase in MR, which induces a large number of spin clusters in Pd-added samples.

关键词： Colossal magnetoresistance Ag-added manganite Pd-added manganite Roomtemperature magnetoresistance spin cluster Polarization of Pd atom

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