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- A. Magnetically ordered materials (1)
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Articles 1 - 8 of 8
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.
The Effect Of Phase Separation On Charge Ordering State In La12xcaxmno3 (X ¼ 1/2, 2/3, And 3/4), H. D. Zhou, G. Li, S. J. Feng, Y. Liu, T. Qian, Xiaojuan Fan, X. G. Li
The Effect Of Phase Separation On Charge Ordering State In La12xcaxmno3 (X ¼ 1/2, 2/3, And 3/4), H. D. Zhou, G. Li, S. J. Feng, Y. Liu, T. Qian, Xiaojuan Fan, X. G. Li
Xiaojuan Fan
The magnetic phase separation characteristics are found in manganese perovskite La1/3Ca2/3MnO3 by electron spin resonance (ESR) and magnetization measurements. An extra resonance signal observed in ESR spectra just above the charge ordering (CO) temperature TCO provides strong evidence for the existence of ferromagnetic (FM) clusters near the CO state. The investigation of the resistivity of La1-xCaxMnO3 (x=1/2, 2/3, and 3/4) in different magnetic fields up to 14 T shows that the effect of magnetic fields on CO state decreases with increasing x. Our results indicate that the percolative characteristics of the phase separation between FM clusters and CO state for …
Absorption Of Microwaves In La1Àxsrxmno3 Manganese Powders Over A Wide Bandwidth, G. Li, G. G. Hu, H. D. Zhou, Xiaojuan Fan, X. G. Li
Absorption Of Microwaves In La1Àxsrxmno3 Manganese Powders Over A Wide Bandwidth, G. Li, G. G. Hu, H. D. Zhou, Xiaojuan Fan, X. G. Li
Xiaojuan Fan
We present the frequency dependence of microwave-absorbing properties of La1-xSrxMnO3 (x=0.4, 0.5, 0.6, and 0.7) powders at room temperature. The absorbing properties change gradually with x in the frequency range of 8–12 GHz. The optimal absorption can be achieved for a x=0.4 sample and its microwave loss peak value is about 25 dB. Further experimental results show that the absorption can be attributed to magnetic and dielectric losses and the microwave loss peak corresponds to the maximum dielectric loss tangent tan δe near 10.5 GHz. Furthermore, the absorbing properties of the oxides mixed with …
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 …
Contact Printed Co/Insulator/Co Molecular Junctions, Xiaojuan Fan, David L. Rogow, Claudia H. Swanson, Akhilesh Tripathi, Scott R. J. Oliver
Contact Printed Co/Insulator/Co Molecular Junctions, Xiaojuan Fan, David L. Rogow, Claudia H. Swanson, Akhilesh Tripathi, Scott R. J. Oliver
Xiaojuan Fan
The authors report the contact printing of a Au/Co double layer (total thickness ∼20–40nm) onto a self-assembled monolayer surface to form molecular junctions under ambient conditions. The feature size ranges from 50×50μm2 to 2×2 mm2. Grazing incident x-ray diffraction of the multilayer junction shows all expected Au peaks, while elemental Co was confirmed by energy dispersive spectroscopy. Film thickness, roughness, and density were characterized by x-ray reflectivity. I-V measurements show a prominent hysteresis, likely associated with charge trapping at the metal-organic interface, not an intrinsic feature of alkanedithiol molecules.
Direct Observation Of Magnetic Domains In Phase Separated Nd0.7ca0.3mno3 Single Crystals, Xiaojuan Fan, Hideomi Koinuma, Tetsuya Hasegawa
Direct Observation Of Magnetic Domains In Phase Separated Nd0.7ca0.3mno3 Single Crystals, Xiaojuan Fan, Hideomi Koinuma, Tetsuya Hasegawa
Xiaojuan Fan
The magnetic properties of single-crystalline Nd0.7Ca0.3MnO3 were studied with both macroscopic and microscopic probes. The magnetization shows large irreversibility behavior between zero-field-cooled and field-cooled data at low field, suggesting a phase separation driven by competition between ferromagnetic and antiferromagnetic phases. The scanning superconducting quantum interference device microscope observations under zero field gave clear evidence that the compound includes ferromagnetic regions as the ground state below Tc. It was also found that two different phase-separated states appear, depending on temperature. At T∼125 K, weak but finite spontaneous magnetization develops, while the magnetization is abruptly enhanced below 95 K, possibly reflecting an …
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.