Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 4 of 4
Full-Text Articles in Physical Sciences and Mathematics
Transport Properties Of The La1−Xcaxmno3 (0.5 ≤ X < 1), H. Zhou, R. Zheng, G. Li, S. Feng, Xiaojuan Fan, X. Lia
Transport Properties Of The La1−Xcaxmno3 (0.5 ≤ X < 1), H. Zhou, R. Zheng, G. Li, S. Feng, Xiaojuan Fan, X. Lia
Xiaojuan Fan
The transport properties of the La1−xCaxMnO3 (0.5 ≤ x < 1) system in magnetic fields up to 14 T were studied. We found that the relationship between the charge ordering temperature TCO and Mn4+ content nMn4+ obeys the formula TCO/Tmax = 1−a(nMn4+ −n0)2, here n0 and a are constants and Tmax is the maximum of TCO. For x = 0.65, TCO arrives at the maximum value of 249.5 K in zero magnetic field, while the charge ordered (CO) state is most stable around x = 0.75. For x = 0.5 when H < 6 T the resistivity displays Mott’s variable-range hopping (VRH) behavior, when 6 < H < 12 T it is suggested that two kinds of conduction mechanism, i.e., VRH and magnetic polarons, coexist in the material, and when H > 12 T the resistivity shows metallic-like behavior and the transport mechanism is attributed to coexistence of magnetic polarons and free carriers. For x = 0.95, the conduction mechanism accords with the coexistence of VRH and magnetic polarons.
The Jahn–Teller Effect And Electron–Phonon Interaction In La0.25ca0.75mn1−Xcrxo3, H. Zhou, G. Li, H. Chen, R. Zheng, Xiaojuan Fan, X. Li
The Jahn–Teller Effect And Electron–Phonon Interaction In La0.25ca0.75mn1−Xcrxo3, H. Zhou, G. Li, H. Chen, R. Zheng, Xiaojuan Fan, X. Li
Xiaojuan Fan
The ultrasonic (longitudinal and transverse) velocities and the transport and magnetic properties of polycrystalline La0.25Ca0.75Mn1-xCrxO3 (x = 0, 0.03, 0.05, and 0.07) have been studied systematically. It was found that with increasing Cr content, the resistivity increases, the charge-ordering transition temperature TCO shifts to low temperature, and the magnetic moment of the system is strengthened. From the temperature dependence of the ultrasonic velocities, one can establish that the Jahn-Teller energy and phonon exchange constant decrease with increasing Cr content.
Competition Between Ferromagnetic Metallic And Paramagnetic Insulating Phases In Manganites, G. Li, H. Zhou, S. Feng, Xiaojuan Fan, X. Li, Z. Wang
Competition Between Ferromagnetic Metallic And Paramagnetic Insulating Phases In Manganites, G. Li, H. Zhou, S. Feng, Xiaojuan Fan, X. Li, Z. Wang
Xiaojuan Fan
La0.67Ca0.33Mn1−xCuxO3(x=0 and 0.15) epitaxial thin films were grown on the (100) LaAlO3 substrates, and the temperature dependence of their resistivity was measured in magnetic fields up to 12 T by a four-probe technique. We found that the competition between the ferromagnetic metallic (FM) and paramagnetic insulating (PI) phases plays an important role in the observed colossal magnetoresistance(CMR) effect. Based on a scenario that the doped manganites approximately consist of phase-separated FM and PI regions, a simple phenomenological model was proposed to describe the CMR effect. Using this model, we calculated the resistivity as functions of temperature and magnetic field. The …
Polymer Gel Templating Of Free-Standing Inorganic Monoliths For Photocatalysis, Xiaojuan Fan, Honghan Fei, David Demaree, Daniel Brennan, Jessica St. John, Scott Oliver
Polymer Gel Templating Of Free-Standing Inorganic Monoliths For Photocatalysis, Xiaojuan Fan, Honghan Fei, David Demaree, Daniel Brennan, Jessica St. John, Scott Oliver
Xiaojuan Fan
We have developed a simple, low-cost process to fabricate free-standing porous metal oxide monoliths. Various swollen polymers and hydrogels possessing an open network structure are infiltrated with pure liquid metal alkoxide. Hydrolysis followed by chemical or thermal degradation of the polymer leads to bulk porous monoliths, TiO2 and SiO2 as initial examples. The titania solids were subsequently employed as photocatalysts under UV light and monitored for adsorption. The materials show efficient reusable photocatalytic ability as compared to pure-phase nanoparticle titanium oxide.