Fea00 -~Nix alloys of ultrafine particle with the average grain size of about 10 nm were synthesized by mechanically alloying process. The samples were investigated by X-ray diffraction and measurements of the saturation magnetization and coercivity force. Both b. c. c and f. c. c phase exist within a wide range for Fel00 -~ Ni~, while x~45. The effective magnetic anisotropy K e was measured by applying the law of approach to saturation. The value of K e decreases with an increase of Ni content. It is noticed that the strain anisotropy makes a large contribution to the magnetic anisotropy. The estimation of grain size leads to the determination of the single domain critical size and domain wall energy. The exchange stiffness and exchange integral deduced from the relationship between the effective magnetic anisotropy and domain wall energy are in agreement with that calculated by other methods.
Entanglement is used to measure correlation between separated subsystems, von Netmmnn entropy is used to study evolutions of entanglement of atoms in processes of interaction between atoms with the field prepared in coherent state. The effects of field intensity and detuning on entanglement are investigated. It is shown that the entanglement exhibited oscillations in its evolutions, their amplitudes and mean values decrease with increasing field intensity. Oscillation frequencies increase with detuning, but the maximum values are almost independent of detuning.
The quantum theory of polarizing light and the Stokes operators are applied to the study of the evolutions of polarization states of light in the processes of i nteraction with atoms in the case with or without Kerr medium. The non_classic b ehavior in the fluctuations of Stokes parameters for the polarizing light and th eir squeezing are investigated. The polarization ellipse, the degree of polariza tion of the field in quantum optics and the signal_to_noise ratio in the Stokes parameters are discussed. It is shown that the modulated oscillations appear in the evolutions of Stokes parameters and their fluctuations. These oscillations c ollapse and revive intermittently. The polarization ellipse does not vary in the interaction with atoms but the degree of polarization will oscillate. Kerr medi um changes these oscillations distinctly.
The Hamfltonian of coupled three-level atoms interacting with light field in the cavity filled with Kerr-like medimn is derived. A simplified anal3fde solution to the Sch_r6dinger equation of the system is obtained. The case of A type atom with degenerate lower leveis is discussed in detail. It is shown that the coupling strength between atoms and Kerr coefficient affect the system' s dynamic behaviors, especially the modulation period and oscillation frequency of the squeezing parametem of the field and the collective dipole moment. Dynamic behaviors of the system are sensitive to the ~ state of atoms.
Special kinds of generalized superposition states, superposition coherent states, are studied in this paper. These states can be produced by superposing a pair of coherent states [ a) and I -a). Their quantum statistical properties, the fluctuations of field and squeezing have been discussed in detail. These properties are dependent on superposition phase. We also describe the squeezing regions in phase space for these states.
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