Mesoscopic Fano effect modulated by Rashba spin-orbit coupling and external magnetic field

By employing non-equilibrium Green's function method, the mesoscopic Fano effect modulated by Rashba spin-orbit (SO) coupling and external magnetic field has been elucidated for electron transport through a hybrid system composed of a quantum dot (QD) and an Aharonov-Bohm (AB) ring. The results show that the orientation of the Fano line shape is modulated by the Rashba spin-orbit interaction k(R)L variation, which reveals that the Fano parameter q will be extended to a complex number, although the system maintains time-reversal symmetry (TRS) under the Rashba SO interaction. Furthermore, it is shown that the modulation of the external magnetic field, which is applied not only inside the frame, but also on the QD, leads to the Fano resonance split due to Zeeman effect, which indicates that the hybrid is an ideal candidate for the spin readout device. (C) 2007 Elsevier B.V All rights reserved.

Magnetic properties of tin-doped magnetite nanoparticles

Structural and magnetic characteristics of Fe3-xSnxO4 (x < 0.3) nanoparticles synthesized using the precipitation exchange method have been investigated by X-ray diffraction, transmission electron microscope, Mossbauer spectra, X-ray photoelectron spectroscopy and magnetization measurement. The mean particle dimension decreases from 8 to 6 nm, the lattice parameters enlarge, the saturation magnetization decreases, as well as the magnetization and the coercive field increase, with increasing tin-content. The paramagnetic property of the specimens indicates that the replacement of Fe3+ by Sn4+ on the octahedral sites of Fe3O4 causes a progressive lowering of the Curie temperature and the Curie temperatures of the materials are all lower than that of crystallite tin-doped magnetite. This striking debasing is due to the lessening of the grain size. This is the smallest size reported thus far for paramagnetic tin-doped magnetite particles. (c) 2006 Elsevier B.V. All rights reserved.

Influence of Fe3+ on perovskite oxides: La2/3Ca1/3Mn1-xFexO3

The structure and magnetoresistance properties in sintered samples of La-2/3 Ca-1/3 Mn1-x FexO3 (0 less than or equal to x less than or equal to 0.84) are studied by using Mossbauer spectroscopy, XRD and magnetic measurement. There are antiferromagnetic interactions between Fe and its nearest neighbors (Fe, Mn) when 0 less than or equal to x less than or equal to 0.67, which are important factors influencing the double-exchange between Mn3+ and Mn4+, Curie temperature, magnetic moment and GMR. It is suggested that the Mn3+(Fe3+)/Mn4+ system also consists of magnetic clusters with different sizes.

Crystallographic and magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

The crystallographic and intrinsic magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) have been investigated. The lattice constants and the unit cell volume of R3Fe29-xTxHy decrease with increasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Regular anisotropic expansions, mainly along the a- and b-axis rather than along the c-axis, are observed for all the compounds upon hydrogenation. Hydrogenation leads to an increase in Curie temperature. First-order magnetization processes (FOMP) occur in magnetic fields of around 1.5 T and 4.0 T at 4.2 K for Nd3Fe24.5Cr4.5H5.0 and Tb(3)Fc(27.0)Cr(2.0)H(2.8), and around 1.4 T at room temperature for Gd3Fe28.0Cr1.0H4.2 Abnormal crystallographic and magnetic properties of Ce3Fe29-xTxHy suggest that the Ce ion is non-triply ionized.

Structural and magnetic properties of hydrides R3Fe29-xVxHy (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

A systematic investigation of crystallographic and intrinsic magnetic properties of the hydrides R3Fe29 - xVxHy (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed in this work. The lattice constants a, b, and c and the unit cell volume of R3Fe29 - xVxHy decrease with increasing rare-earth atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Hydrogenation results in regular anisotropic expansions along the a-, b-, and c-axes in this series of hydrides. Abnormal crystallographic and magnetic properties of Ce3Fe27.5V1.5H6.5, like Ce3Fe27.5V1.5, suggest that the Ce ion is non-triply ionized. Hydrogenation leads to the increase in both Curie temperature for all the compounds and in the saturation magnetization at 4.2 K and RT for R3Fe29 - xVx with R = Y, Ce, Nd, Sm, Gd, and Dy, except for Tb. Hydrogenation also leads to a decrease in the anisotropy field at 4.2 K and RT for R3Fe29 - xVx with R = Y, Ce, Nd, Gd, Tb, and Dy, except for Sm. The Ce3Fe27.5V1.5 and Gd3Fe28.4V0.6 show the larger storage of hydrogen with y = 6.5 and 6.9 in these hydrides. (C) 1998 Elsevier Science B.V. All rights reserved.

Crystallographic and magnetic properties of the hydrides R3Fe29-xCrxHy (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy)

A systematic study of the structural and intrinsic magnetic properties of the hydrides R3Fe29-xCrxHy (R = Y, Ce, Nd, Sm, Gd, Tb, and Dy) has been performed. Hydrogenation lends to a relative volume expansion of the unit cell and a decrease in x-ray density for each compound. Anisotropic expansions mainly along the n- and b-axes rather than along the c-axis for all of the compounds upon hydrogenation are observed. The lattice constants and the unit-cell volume of R3Fe29-xCrx and R3Fe29-xCrxHy decrease with increasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Hydrogenation results in an increase in the Curie temperature and a corresponding increase in the saturation magnetization at room temperature for each compound. After hydrogenation a decrease of 0.34 mu(B)/Fe in the average Fe atomic magnetic moment and a slight increase in the anisotropy field for Y3Fe27.2Cr1.8 are achieved at 4.2 K. First-order magnetization processes (FOMP) occur in magnetic fields of around 1.5 T and 4.0 T at 4.2 K for Nd3Fe24.5Cr4.5H5.0 and TD3Fe27.0Cr2.0H2.8, and around 1.4 T at room temperature for Gd3Fe28.0Cr1.0H4.2. The abnormal crystallographic and magnetic properties of Ce3Fe25.0Cr4.0 and Ce3Fe25.0Cr4.0H5.4 suggest that the Ce ion non-triply ionized.

Crystallographic and magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

The crystallographic and intrinsic magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) have been investigated. The lattice constants and the unit cell volume of R3Fe29-xTxHy decrease with increasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Regular anisotropic expansions, mainly along the a- and b-axis rather than along the c-axis, are observed for all the compounds upon hydrogenation. Hydrogenation leads to an increase in Curie temperature. First-order magnetization processes (FOMP) occur in magnetic fields of around 1.5 T and 4.0 T at 4.2 K for Nd3Fe24.5Cr4.5H5.0 and Tb(3)Fc(27.0)Cr(2.0)H(2.8), and around 1.4 T at room temperature for Gd3Fe28.0Cr1.0H4.2 Abnormal crystallographic and magnetic properties of Ce3Fe29-xTxHy suggest that the Ce ion is non-triply ionized.

Study of a magnetic alloy-loaded RF cavity for bunch compression at the CSR

The Heavy Ion Research Facility and Cooling Storage Ring (HIRFL-CSR) accelerator in Lanzhou offers a unique possibility for the generation of high density and short pulse heavy ion beams by non-adiabatic bunch compression longitudinally, which is implemented by a fast jump of the RF-voltage amplitude. For this purpose, an RF cavity with high electric field gradient loaded with Magnetic Alloy cores has been developed. The results show that the resonant frequency range of the single-gap RF cavity is from 1.13 MHz to 1.42 MHz, and a maximum RF voltage of 40 kV with a total length of 100 cm can be obtained, which can be used to compress heavy ion beams of U-238(72+) with 250 MeV/u from the initial bunch length of 200 ns to 50 ns with the coaction of the two single-gap RF cavity mentioned above.

Preparation of ferrite MFe2O4 (M = Co, Ni) ribbons with nanoporous structure and their magnetic properties

Spinel ferrite, MFe2O4 (M = Co, Ni), ribbons with nanoporous structure were prepared by electrospinning combined with sol-gel technology. The ribbons were formed through the agglomeration of magnetic nanoparticles with PVP as the structure directing template. The length of the polycrystalline ribbons can reach millimeters, and the width of the ribbons can be tuned from several micrometers to several hundred nanometers by changing the concentration of precursor. The nanoporous structure was formed during the decomposition of PVP and inorganic salts.

Erbium-Complex-Doped Near-Infrared Luminescent and Magnetic

A near-infrared luminescent macroporous material (PL-Macromaterial) and a near-infrared luminescent/magnetic bifunctional macroporous material (MML-Macromaterial) were synthesized by using polystyrene microspheres (PS) and Fe3O4 @polystyrene core-shell nanoparticles (Fe3O4@PS), respectively, as templates. Both the PL-Macromaterial and the M/PL-Macromaterial show the characteristic emission of the Er 3, ion. Moreover, the M/PL-Macromaterial possesses superparamagnetic properties at room temperature.

Magnetic Mesoporous Silica Spheres for Drug Targeting and Controlled Release

Magnetically functionalized mesoporous silica spheres with different size (average diameter, A.D.) from 150 nm to 2 mu m and pore size distribution were synthesized by generating magnetic FexOy nanoparticles onto the mesoporous silica hosts using the sol-gel method. The X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), N-2 adsorption/desorption results show that these composites conserved regular sphere morphology and ordered mesoporous structure after the formation of FexOy nanoparticles. XRD and X-ray photoelectron spectroscopy (XPS) analysis confirmed that the FexOy generated in these mesoporous silica hosts is mainly composed of gamma-Fe2O3. Magnetic measurements reveal that these composites with different gamma-Fe2O3 loading amounts possess super-paramagnetic properties at 300 K, and the saturation magnetization increases with increasing Fe ratio loaded.

Particle Size-Dependent Charge Ordering and Magnetic Properties in Pr0.55Ca0.45MnO3

A series of Pr0.55Ca0.45MnO3 compounds with average particle size ranging from 2000 to 30 nm have been synthesized by the sol-gel method and their charge ordering (CO) and magnetic properties are investigated. It is observed that with particle size decreasing, the CO transition is gradually suppressed and finally disappears upon particle size down to 35 nm, while the ferromagnetism (FM) emerges and exhibits a nonmonotonous variation with a maximum at 45 nm samples. The FM components in all samples never reach long-range ordering but rather only show short-range clusters. A new explanation considering the coupling between lattice, charge, and spin in the system is raised to understand the suppression of the CO state, Both the competition between the CO/AFM and FM states and the core-shell model are employed to explain the variation of the FM phase. These results may provide a deeper insight into the physics of particle size effect on the charge ordering manganite.

Tunable synthesis, growth mechanism, and magnetic properties of La0.5Ba0.5MnO3

La0.5Ba0.5MnO3 products with novel flowerlike, microcube, and nanocube structures were successfully synthesized by a simple hydrothermal route by controlling the alkalinity of the reaction solutions. The synthesized products were systematically studied by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The results showed that the formation of the flowerlike structures with a layer assembly experienced a nucleation-aggregation-crystallization growth process, while the cubic structures experienced a nucleation-crystallization growth process due to the effect of different alkalinity in the reaction solutions. The higher alkalinity also led to a decrease in the size in the cubic structures. Suitable temperature and pressure were demonstrated to be crucial to the formation of the flowerlike structures by carrying out further control experiments. The measurement of the magnetic properties of three samples obtained at different alkaline conditions indicated that the size of the La0.5Ba0.5MnO3 products had an obvious influence on their properties; however, the dependence of the properties upon the morphology of the La0.5Ba0.5MnO3 products was minor.

Preparation of nanocrystalline NiZnCu ferrite particles by sol-gel method and their magnetic properties

Polyvinyl alcohol (PVA) was first used as chelating agent and metal nitrates as precursor of ferrite in the fabrication of nanocrystalline Ni0.65Zn0.35Cu0.1Fe1.9O4 particles by the sol-gel method. The thermal decomposition process of dried gel was studied by thermogravimetry (TG), differential thermal analysis (DTA) and infrared spectra (IR). The structural and magnetic properties of resultant particles were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and Mossbauer spectroscopy. The dependence of the decomposition of dried gel, the formation of spinel structured NiZnCu ferrite, the sizes of annealed particles, the saturation magnetization and coercivity of annealed particles on annealing temperature is presented.