The Singularity Paramagnetic Peak of Bi0.3Sb1.7Te3 with p-type Surface State

The magnetization measurement was performed in the Bi0.3Sb1.7Te3 single crystal. The magnetic susceptibility revealed a paramagnetic peak independent of the experimental temperature variation. It is speculated to be originated from the free-aligned spin texture at the Dirac point. The ARPES reveals that the Fermi level lies below the Dirac point. The Fermi wavevector extracted from the de Haas–van Alphen oscillation is consistent with the energy dispersion in the ARPES. Our experimental results support that the observed paramagnetic peak in the susceptibility curve does not originate from the free-aligned spin texture at the Dirac point.

Modulating light absorption and multiferroic properties of BiFeO3-based ferroelectric films by the introduction of ZnO layer

Pure bismuth ferrite (BiFeO3, BFO) and ZnO thin films, as well as BFO/ZnO and ZnO/BFO composite thin films were successfully deposited by a sol-gel process on Pt/Ti/SiO2/Si and FTO/glass substrates, respectively. The chemical composition, surface morphology, optical properties, and multiferroicity were systematically investigated. X-ray diffraction and electron microscopy measurements were used to determine the crystalline phase and to analyze the surface morphology. Evidently, the absorption edges of both BFO/ZnO and ZnO/BFO films show a redshift, broadening the absorption range. The leakage current density decreases with the introduction of ZnO, and the ferroelectricity was significantly improved of the bilayers. Thereinto, BFO/ZnO and ZnO/BFO show the highest saturate polarization (2P s) of 46.7 μc/cm2 and the maximum remanent polarization (2P r) of 18.5 μc/cm2, respectively. Meanwhile, the magnetization measurement revealed that both BFO/ZnO and ZnO/BFO exhibiting an enhanced magnetization, especially, BFO/ZnO displays the highest saturation magnetization (2M s, 68.87 emu/cm3) and remanent magnetization (2M r, 4.87 emu/cm3).

Magnetic behavior of Magneto-Rheological Foam under Uniaxial Compression Strain

This study reports the development of a Magneto-Rheological Foam, which consists in a porous matrix filled by ferromagnetic particles. The porous matrix of such a composite being easily deformable, large magnetic properties changes are expected. The measurements of the magnetic properties of such a Magneto-Rheological Foam submitted to a compressive strain are reported. Main aspect of the magnetic properties is the low field magnetic permeability as the function of the compression and filling factor. Then, larger field magnetization measurement allowed to investigate the saturation field as a function of the filling factor. Because of the large amount of pores in the material, the magnetic relative permeability, µr, is quite small (µr ~1). However, these materials can be easily deformed over a large range of strain providing important relative variation of the magnetic properties under mechanical solicitation. The composite magnetic permeability is increasing under compression for all the considered filling factors. A model is then developed to understand the variation of the permeability with the strain. Hence, from a simple concept consisting of taking advantage of high deformation of foams, the present study demonstrates the interest of such a highly compressible while cheap composite for obtaining a large magneto-rheological effect.

Structure and magnetic characterization of Sr-doped BiFeO3 prepared by sol–gel method

Multiferroic nanocrystalline Bi[Formula: see text]Sr[Formula: see text]FeO3 ([Formula: see text], 0.05, 0.1) samples were synthesized using the sol–gel method and characterized by powder X-ray diffraction, Mössbauer spectroscopy and SQUID system. The small-angle X-ray diffraction analysis showed that the sample underwent phase transition from rhombohedral to pseudo-cubic structure with the enhancement of Sr content. In addition, impurity peaks gradually diminished, indicating that content of impurities of samples reduced. Furthermore, it can be determined that there is only Fe[Formula: see text] in all the samples and impurity phase that existed in the samples was Bi[Formula: see text]FeO[Formula: see text] by fitting Mössbauer spectra. It is further confirmed that Bi[Formula: see text] Sr[Formula: see text]FeO3 samples were generated by oxygen vacancy equilibrium valence state when Sr[Formula: see text] ions replaced Bi[Formula: see text] ions. The change of quadrupole splitting indicated that a low concentration of Sr[Formula: see text] ions diffused homogeneously in the sample. Magnetization measurement showed that the magnetization of the sample increased gradually with the substitution of Bi[Formula: see text] by nonequivalent Sr[Formula: see text] ions, which can be ascribed to the decrease of grain size and the increase of oxygen vacancy and specific surface in the samples.

Structural, Chemical and Low Temperature Magnetic Properties of Lead Free 0.6NiFe2O4 - 0.4Na0.5Bi0.5TiO3 Magnetoelectric Composite

We report on structural, chemical and low temperature magnetic properties of lead free 0.6NiFe2O4 - 0.4Na0.5Bi0.5TiO3 composite. NiFe2O4 (NFO) and Na0.5Bi0.5TiO3 (NBTO) are seen to crystallize in inverse spinel and perovskite structure respectively. 0.6NiFe2O4 - 0.4Na0.5Bi0.5TiO3 composite exhibits both NFO and NBTO phases in appropriate composition. Zero field cooled (ZFC) and field cooled (FC) magnetization measurements carried out from 15 K to 300 K shows a large bifurcation at room temperature. ZFC and FC magnetization measurement exhibit a hump at Tm ⁓ 259.5 K, indicates the possible existence of competing magnetic interactions in 0.6NiFe2O4 - 0.4Na0.5Bi0.5TiO3 composite. Saturation magnetization, remanent magnetization and coercivity values are observed to increase with decreasing the temperature. Temperature dependent saturation magnetization is fit to the Bloch’s law. Magnetocrystalline anisotropy (K1) value at various temperatures are estimated and is seen to increase from 0.23 x104 erg/cc (at 300 K) to 0.34 x104 erg/cc (at 15 K).

Lower Critical Field of Layered Organic Superconductor with Asymmetrical Donor κ-(MDT-TTF)2AuI2

We report magnetization measurement in the superconducting state of a type-II organic layered superconductor with asymmetrical donor k-(MDT-TTF)2AuI2. The demagnetization factor of a plate-like shape of the single crystal has been taken into account for the measurement by applying an external field perpendicular to the conducting plane. The superconducting transition temperature TC is determined to be 4.7 K through the detection of demagnetization signal. The lower critical field is 10.5±1.4 G. This result implies that the stable vortex state of k-(MDT-TTF)2AuI2 can be reached at the applied magnetic field above 105 Oe

The Study of Coexistance of Superconductivity and Spin Glass in Fe Pnictide(Fe1+YSeXTe1−X)

Superconductivity and magnetism were previously thought as incompatible until the discovery of some rare earth ternary compounds that shows the coexistence of superconductivity and magnetism. In some of the recently discovered iron based layered superconductors superconductivity and diamagnetic order system are coexist. That occurs in only 11 and 122 family. The present works we examine the possibility of coexistence of superconductivity and disorder of magnetic spin is called spin glass when freeze the system that can show the superconductivity and spin glass coexist. In this present work we can examine the possibility of coexistence of superconductivity and spin glass in detailed 11 family of Fe1+ySexTe1−x compound. We show that spin glass like behavior is present in FST for x = 0.1 - 0.15 we present evidence form magnetization measurement and characterized the short-range order with neutron scattering. One of our main results is that the short-range order is structural as well as magnetic order. The factor of magnetic order exchange in long range depend on temperature, pressure, number of doping and other external factor discussed it. We found mathematical expression for superconductor transition TC, spin glass temperature TgSusceptibility x(q), and retardation time τ using for born approximation and digamma function depend on wave vector(q) and cut off frequency(ω) in the region coexistence of superconductivity and spin glass in Fe1+ySexTe1−xcompound.