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Ferromagnetic properties have been observed in CuO doped with 3.5-15 at. \% of Mn. The transition from ferromagnetic to paramagnetic phase at T-C=80 K is associated with the metal-insulator transition. Magnetoresistance is weakly negative in the vicinity of the transition, but positive in a wide range of temperatures below T-C. The experimental results suggest a possibility of interpretation in terms of the Zener double-exchange mechanism and strong electron-phonon interactions. (C) 2003 American Institute of Physics.

Ferromagnetic properties have been observed in CuO doped with 3.5-15 at. \% of Mn. The transition from ferromagnetic to paramagnetic phase at T-C=80 K is associated with the metal-insulator transition. Magnetoresistance is weakly negative in the vicinity of the transition, but positive in a wide range of temperatures below T-C. The experimental results suggest a possibility of interpretation in terms of the Zener double-exchange mechanism and strong electron-phonon interactions. (C) 2003 American Institute of Physics.

Ferromagnetic properties have been observed in CuO doped with 3.5-15 at. \% of Mn. The transition from ferromagnetic to paramagnetic phase at T-C=80 K is associated with the metal-insulator transition. Magnetoresistance is weakly negative in the vicinity of the transition, but positive in a wide range of temperatures below T-C. The experimental results suggest a possibility of interpretation in terms of the Zener double-exchange mechanism and strong electron-phonon interactions. (C) 2003 American Institute of Physics.

Co-3(BO3)(2)/surfactant composites have been prepared by the controlled precipitation of aqueous cobalt cations together with surfactant. The composite shows a layered structure as determined by x-ray diffraction, in which the Co-3(BO3)(2) layers of about 6 Angstrom in thickness are in alternation with surfactant bilayers. The temperature-dependent magnetization measured in the zero-field-cooled (ZFC) and field-cooled (FC) processes and the AC-magnetic susceptibility measured at different frequencies indicate that there is a freezing temperature at low temperature (<6 K) and the temperature is weakly frequency dependent. A clear difference between thermal remanent magnetization (TRM) and isothermal remanent magnetization (IRM) was observed at 2 K. All the experimental observations suggest that the multilayers are spinglass in nature.

Co-3(BO3)(2)/surfactant composites have been prepared by the controlled precipitation of aqueous cobalt cations together with surfactant. The composite shows a layered structure as determined by x-ray diffraction, in which the Co-3(BO3)(2) layers of about 6 Angstrom in thickness are in alternation with surfactant bilayers. The temperature-dependent magnetization measured in the zero-field-cooled (ZFC) and field-cooled (FC) processes and the AC-magnetic susceptibility measured at different frequencies indicate that there is a freezing temperature at low temperature (<6 K) and the temperature is weakly frequency dependent. A clear difference between thermal remanent magnetization (TRM) and isothermal remanent magnetization (IRM) was observed at 2 K. All the experimental observations suggest that the multilayers are spinglass in nature.

Co-3(BO3)(2)/surfactant composites have been prepared by the controlled precipitation of aqueous cobalt cations together with surfactant. The composite shows a layered structure as determined by x-ray diffraction, in which the Co-3(BO3)(2) layers of about 6 Angstrom in thickness are in alternation with surfactant bilayers. The temperature-dependent magnetization measured in the zero-field-cooled (ZFC) and field-cooled (FC) processes and the AC-magnetic susceptibility measured at different frequencies indicate that there is a freezing temperature at low temperature (<6 K) and the temperature is weakly frequency dependent. A clear difference between thermal remanent magnetization (TRM) and isothermal remanent magnetization (IRM) was observed at 2 K. All the experimental observations suggest that the multilayers are spinglass in nature.

Er3+- and Yb3+- ions-co-doped silica thin films were prepared by RF magnetron sputtering. Enhanced photoluminescence centered at 1.534 mu m was detected at room temperature when excited by a Nd-YAG laser lint at 1.064 mu m. The photoluminescence intensity increases with Yb-atom doped concentration and tends to saturate at the Yb-atom concentration of 3.0\%. indicating that the enhanced photoluminescence results from the energy transfer from Yb3+ to Er3+. (C) 1999 Elsevier Science S.A. All rights reserved.

Er3+- and Yb3+- ions-co-doped silica thin films were prepared by RF magnetron sputtering. Enhanced photoluminescence centered at 1.534 mu m was detected at room temperature when excited by a Nd-YAG laser lint at 1.064 mu m. The photoluminescence intensity increases with Yb-atom doped concentration and tends to saturate at the Yb-atom concentration of 3.0\%. indicating that the enhanced photoluminescence results from the energy transfer from Yb3+ to Er3+. (C) 1999 Elsevier Science S.A. All rights reserved.

Er3+- and Yb3+- ions-co-doped silica thin films were prepared by RF magnetron sputtering. Enhanced photoluminescence centered at 1.534 mu m was detected at room temperature when excited by a Nd-YAG laser lint at 1.064 mu m. The photoluminescence intensity increases with Yb-atom doped concentration and tends to saturate at the Yb-atom concentration of 3.0\%. indicating that the enhanced photoluminescence results from the energy transfer from Yb3+ to Er3+. (C) 1999 Elsevier Science S.A. All rights reserved.

We report the results of our degenerate four-wave-mixing measurements (DFWM) on the fullerene series from C-60 to C-96 dissolved in CS2. The DFWM measurements were carried out using 70 ps laser pulses at the wavelength of 0.532 mu m under the optimized experimental conditions. The second hyperpolarizabilities gamma(1111) of all these fullerenes were determined to be on the order of 10(-31)-10(-30) esu, and overall they increase smoothly with the carbon cage size except for C-70 and C-78, which show anomalously larger gamma(1111) values than those of their neighboring cage sizes we investigated. The number of pi-conjugated electrons, geometrical structure, and resonance enhancement are discussed as possible factors responsible for the observed third-order optical nonlinearities of the fullerenes.

Dy@C-82 has been prepared by an efficient solvent extraction procedure and characterized by negative-ion desorption chemical ionization mass spectrometry and UV-VIS-near-IR absorption. Degenerate four-wave-mixing measurements on the CS2 solution of Dy@C-82 were performed using 70 ps laser pulses at 0.532 mu m. The magnitude of the second hyperpolarizability gamma(1111) of the Dy@C-82 molecule was (3.0 +/- 0.5)x 10(-30) esu at 0.532 mu m. The resonant enhancement and the electron transfer from the trapped dysprosium to the C,, cage are suggested to bring about its larger non-linear optical response relative to the empty fullerene. The experimental results are in good agreement with our calculations based on an extended Su-Schrieffer-Heeger model and the sum-over-state method. (C) 1998 Elsevier Science B.V. All rights reserved.

We report the results of our degenerate four-wave-mixing measurements (DFWM) on the fullerene series from C-60 to C-96 dissolved in CS2. The DFWM measurements were carried out using 70 ps laser pulses at the wavelength of 0.532 mu m under the optimized experimental conditions. The second hyperpolarizabilities gamma(1111) of all these fullerenes were determined to be on the order of 10(-31)-10(-30) esu, and overall they increase smoothly with the carbon cage size except for C-70 and C-78, which show anomalously larger gamma(1111) values than those of their neighboring cage sizes we investigated. The number of pi-conjugated electrons, geometrical structure, and resonance enhancement are discussed as possible factors responsible for the observed third-order optical nonlinearities of the fullerenes.

Dy@C-82 has been prepared by an efficient solvent extraction procedure and characterized by negative-ion desorption chemical ionization mass spectrometry and UV-VIS-near-IR absorption. Degenerate four-wave-mixing measurements on the CS2 solution of Dy@C-82 were performed using 70 ps laser pulses at 0.532 mu m. The magnitude of the second hyperpolarizability gamma(1111) of the Dy@C-82 molecule was (3.0 +/- 0.5)x 10(-30) esu at 0.532 mu m. The resonant enhancement and the electron transfer from the trapped dysprosium to the C,, cage are suggested to bring about its larger non-linear optical response relative to the empty fullerene. The experimental results are in good agreement with our calculations based on an extended Su-Schrieffer-Heeger model and the sum-over-state method. (C) 1998 Elsevier Science B.V. All rights reserved.

We report the results of our degenerate four-wave-mixing measurements (DFWM) on the fullerene series from C-60 to C-96 dissolved in CS2. The DFWM measurements were carried out using 70 ps laser pulses at the wavelength of 0.532 mu m under the optimized experimental conditions. The second hyperpolarizabilities gamma(1111) of all these fullerenes were determined to be on the order of 10(-31)-10(-30) esu, and overall they increase smoothly with the carbon cage size except for C-70 and C-78, which show anomalously larger gamma(1111) values than those of their neighboring cage sizes we investigated. The number of pi-conjugated electrons, geometrical structure, and resonance enhancement are discussed as possible factors responsible for the observed third-order optical nonlinearities of the fullerenes.

Degenerate four-wave-mixing measurements on C-90 in CS2 with different concentrations were performed using 70 ps laser pulses at 0.532 mu m. The dependence of the conjugate signal intensity on the incident laser power and the concentration of C-90 were investigated, By optimizing experimental parameters, the second hyperpolarizability gamma(1111) of C-90 was determined to be (1.8 +/- 0.6) X 10(-30) esu, which is approximately eight times that of the C-60 molecule measured under identical conditions. Our results are in accord with the theoretical prediction that higher fullerenes should show larger nonlinear optical responses. (C) 1997 Elsevier Science B.V.

Degenerate four-wave-mixing measurements (DFWM) on the metallofullerene Nd@C-82 in CS2 with different concentrations were performed using 70-psec laser pulses at 0.532 mu m. By optimizing experimental parameters, the second hyperpolarizability gamma(1111) of Nd@C-82 was determined to be (2.7 +/- 0.5) x 10(-30) esu, which is over an order of magnitude larger than that of the C-60 molecule measured under the identical conditions.

Photoluminescence (PL) and photoluminescence excitation (PLE) studies have been performed on C-60 confined in NiY zeolite. Besides the Pt, peaks of Ni ions a new peak at 544 nm was observed, which is believed to originate from the trapped C-60 within a NiY molecular sieve. From PLE measurements, the transfer of carriers from Ni ions to their adjacent C-60 molecules is deemed to be responsible for the PL and its enhancement. PLE, PL and EPR measurements indicate the coordination of Ni ions on C-60 molecules in supercages of NiY zeolite. (C) 1997 Elsevier Science B.V.

Degenerate four-wave-mixing measurements (DFWM) on the metallofullerene Nd@C-82 in CS2 with different concentrations were performed using 70-psec laser pulses at 0.532 mu m. By optimizing experimental parameters, the second hyperpolarizability gamma(1111) of Nd@C-82 was determined to be (2.7 +/- 0.5) x 10(-30) esu, which is over an order of magnitude larger than that of the C-60 molecule measured under the identical conditions.

Photoluminescence (PL) and photoluminescence excitation (PLE) studies have been performed on C-60 confined in NiY zeolite. Besides the Pt, peaks of Ni ions a new peak at 544 nm was observed, which is believed to originate from the trapped C-60 within a NiY molecular sieve. From PLE measurements, the transfer of carriers from Ni ions to their adjacent C-60 molecules is deemed to be responsible for the PL and its enhancement. PLE, PL and EPR measurements indicate the coordination of Ni ions on C-60 molecules in supercages of NiY zeolite. (C) 1997 Elsevier Science B.V.

Degenerate four-wave-mixing measurements on C-90 in CS2 with different concentrations were performed using 70 ps laser pulses at 0.532 mu m. The dependence of the conjugate signal intensity on the incident laser power and the concentration of C-90 were investigated, By optimizing experimental parameters, the second hyperpolarizability gamma(1111) of C-90 was determined to be (1.8 +/- 0.6) X 10(-30) esu, which is approximately eight times that of the C-60 molecule measured under identical conditions. Our results are in accord with the theoretical prediction that higher fullerenes should show larger nonlinear optical responses. (C) 1997 Elsevier Science B.V.

Degenerate four-wave-mixing measurements (DFWM) on the metallofullerene Nd@C-82 in CS2 with different concentrations were performed using 70-psec laser pulses at 0.532 mu m. By optimizing experimental parameters, the second hyperpolarizability gamma(1111) of Nd@C-82 was determined to be (2.7 +/- 0.5) x 10(-30) esu, which is over an order of magnitude larger than that of the C-60 molecule measured under the identical conditions.

Degenerate four-wave-mixing measurements on C-90 in CS2 with different concentrations were performed using 70 ps laser pulses at 0.532 mu m. The dependence of the conjugate signal intensity on the incident laser power and the concentration of C-90 were investigated, By optimizing experimental parameters, the second hyperpolarizability gamma(1111) of C-90 was determined to be (1.8 +/- 0.6) X 10(-30) esu, which is approximately eight times that of the C-60 molecule measured under identical conditions. Our results are in accord with the theoretical prediction that higher fullerenes should show larger nonlinear optical responses. (C) 1997 Elsevier Science B.V.

Photoluminescence (PL) and photoluminescence excitation (PLE) studies have been performed on C-60 confined in NiY zeolite. Besides the Pt, peaks of Ni ions a new peak at 544 nm was observed, which is believed to originate from the trapped C-60 within a NiY molecular sieve. From PLE measurements, the transfer of carriers from Ni ions to their adjacent C-60 molecules is deemed to be responsible for the PL and its enhancement. PLE, PL and EPR measurements indicate the coordination of Ni ions on C-60 molecules in supercages of NiY zeolite. (C) 1997 Elsevier Science B.V.