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刘晓峻 《中国物理快报》2005,22(10):2666-2669
We investigate the photoinduced resistance change (ΔR/R) in a La0.6Sr0.4MnO3 film (Tc~325 K) at different applied dc currents I (0.1-2.0mA) at 295K. At I = 0.1 mA, we have found a significant photoinduced ΔR/ R 17% under photo-irradiation at excitation energy Eexc=3.05 eV and pump power Ppump =2.5 mJ/cm^2, which has been ascribed to the photo-excited down-spin eg carriers and hence the spin-disorder in the ferromagnetic metallic state. With increasing applied electric current to 2.0 mA, the magnitude of the photoinduced ΔR/ R is reduced to 3%, which may be attributed to current-induced ordering of the localized spins.  相似文献
2.
We investigate the photoinduced effects on the electronic structure for half-metallic ferromagnet CrO2 (Tc 390 K), in which the conducting electrons are totally polarized, by using the LSDA+U method. A significant change is found for the band structure and the density of states (DOS) for CrO2 under photo-excitation, especially for the Cr 3dt2g band: disappearance of the spin-split band, suggesting collapse of the half-metallic state. We ascribe the change of electronic structure under photo-excitation to the wider one-electron band W via the strong hybridization of the down-spin Cr 3d and O 2p states. Furthermore we discuss the magnetic properties under photo-excitation.  相似文献
3.
Thermal diffusivity has been investigated in a manganite thin film La0.6Sr0.4MnO3 by means of transient grating (TG) technique at room temperature. A new method, which is generalized to two-layered samples of the thin film deposited on a semi-infinite substrate, is established to fit the TG signals. The thermal diffusivity of the Lao.6Sro.4MnO3 thin film with a thickness of 200nm on an MgO (100) substrate is determined to be 0.92mm^2/s, which is slightly smaller than that of the single crystal sample (1 mm^2/s).  相似文献
4.
Resistivity, thermal diffusivity, lattice and magnetic properties of double perovskite Sr2-xLaxMnMoO6 are investigated with systematic change of La doping concentration x from 0.0 to 0.4. The insulator to metal phase transition is observed with increasing x above 0.3, suggesting that the extra electrons via substitution of La^3 for Sr^2 ions occupy mainly the conduction Mo-4d band. According to the insulator to metal phase transition, the thermal diffusivity of Sr2-xLaxMnMoO6 enhances from 0.33cm^2/s at x=0.0 to 0.49cm^2/s at x=0.4. We further investigate the La doping effects on the lattice and magnetic properties.  相似文献
5.
A comprehensive electronic phase diagram is derived for mixed-valence gold chloride Cs2Au2Cl6 by means of high-pressure Raman spectroscopy. At all the temperatures investigated (100K≤T≤300 K), applications of pressure induce a phase transition from the mlxed-valence (MV) state to a single-valence (SV) state. In the SV state, a broad Au-Cl stretching band appears at~400 cm^-1 below ~200K. We have interpreted the appearance of the band in terms of formation of the AuX2^--like local lattice distortion, or the bipolarons.  相似文献
6.
刘晓峻  守友浩 《中国物理快报》2003,20(11):2027-2029
Effects of hydrostatic pressure on the mixed-valence (MV) bismuth complex BaBiO3 have been investigated up to ~9 GPa by means of high-pressure Raman scattering and absorption spectra at 300 K. The pressure-induced hardeuing behaviour of the Bi-O stretching mode suggests that the predicted pressure-induced MV to the single-valence (SV) phase change cannot occur. Investigation of absorption spectra with pressure shows the enhanced optical gat Egap, which further indicates the remained MV state of Bi ions.  相似文献
7.
<正>The influences of the anisotropy of the outer spherically anisotropic(SA) layer on the far-field spectra and nearfield enhancements of the silver nanoshells are investigated by using a modified Mie scattering theory.It is found that with the increase of the anisotropic value of the SA layer,the dipole resonance wavelength of the silver nanoshell first increases and then decreases,while the local field factor(LFF) reduces.With the decrease of SA layer thickness, the dipole wavelength of the silver nanoshell shows a distinct blue-shift.When the SA layer becomes very thin,the modulations of the anisotropy of the SA layer on the plasmon resonance energy and the near-field enhancement are weakened.We further find that the smaller anisotropic value of the SA layer is helpful for obtaining the larger near-field enhancement in the Ag nanoshell.The geometric average of the dielectric components of the SA layer has a stronger effect on the plasmon resonance energy of the silver nanoshell than on the near-field enhancement.  相似文献
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