Direct Evidence for Multiferroic Magnetoelectric Coupling in 0.9BiFeO(3)-0.1BaTiO(3)

Magnetic, dielectric and calorimetric studies on 0.9BiFeO(3)-0.1BaTiO(3) indicate strong magnetoelectric coupling. XRD studies reveal a very remarkable change in the rhombohedral distortion angle and a significant shift in the atomic positions at the magnetic T-c due to an isostructural phase transition. The calculated polarization using Rietveld refined atomic positions scales linearly with magnetization. Our results provide the first unambiguous, atomic level evidence for magnetoelectric coupling of intrinsic multiferroic origin in a BiFeO3-based system

Increased low field magnetoresistance in electron doped system Sr0.4Ba1.6−xLaxFeMoO6

Magnetotransport properties of electron doped polycrystalline system Sr0.4Ba1.6−xLaxFeMoO6 are presented in this paper. We have observed increased low field magnetoresistance values with significant Curie temperature increase in the electron doped system Sr0.4Ba1.6−xLaxFeMoO6. The low field magnetoresistance value (at 1000 Oe) in 20% La3+ doped sample is observed to be 2.17% at 300 K. At 0.64 T and 80 K, the magnetoresistance change measured in this sample is 21.4%. This sample also showed 50 K increase in Curie temperature over the pristine sample. The increased low field magnetoresistance values are associated with modified grain boundary barriers of the system. The results confirm the fact that the modification of grain boundary barriers has enough potential to possess high low field magnetoresistance values even in the systems with lower spin polarization values. The role of grain to grain connectivity is observed to be dominantly determining the low field magnetoresistance values in grain to grain tunnel type magnetoresistance

Establishement of the magnetic flux density standard in the range 100 µT to 1000 µT

The magnetic flux density standard in the range 100 μT to 1000 μT has been established using a standard Helmholtz coil. The ambient magnetic field including earth's magnetic field components inside the room and other noises has been compensated to a level of the order of 100 nT. A circular triaxial Helmholtz coil pair of size nearly 800 mm has been used for compensating the ambient magnetic field. The standard Helmholtz coil of size 300 mm has been placed in the geometrical centre of the triaxial Helmholtz coil pair. The magnetic flux density has been measured using triaxial and single axis fluxgate magnetometers. The coil constant of the standard Helmholtz coil has been found to be 850.6808± 0.0036804 μT/A, which is in good agreement with the manufacture's specification viz, 850 μT/A, with an uncertainly of <; ± 0.5 %

Influence of Fe segregation at grain boundaries on the magnetoresistance of Sr2Fe1+delta MoO6 polycrystals

In this paper, we report the influence of Fe impurities on the magnetoresistance (MR) of double perovskite Sr2Fe1+delta MoO6 (0.00 <= delta <= 0.20) system. The significant Fe impurities have been created by two different approaches: one by adding the extra amount of Fe2O3 at starting of the synthesis and other by sintering the pristine Sr2FeMoO6 sample at high temperature (1300 degrees C) in high reducing environment (similar to 8% H-2 + 92% Ar). A remarkable 11% magnetoresistance at room temperature under the presence of low magnetic field (0.72 T) has been observed in the pristine sample. The achieved high low field magnetoresistance value in the sample may be due to the optimized synthesis conditions to get better inter-granular tunneling through grain boundaries. However, the presence of Fe impurity results into the sharp reduction in magnetoresistance because of reduced spin polarized tunneling. The loss of insulating nature of the grain boundaries and the inelastic scattering of the charge carriers through the metallic impurities of iron at grain boundaries may be the reason of reduced spin polarized tunneling

Remarkable influence on the dielectric and magnetic properties of lithium ferrite by Ti and Zn substitution

The effect of Zn and Ti substitution on the magnetic and electrical properties of Li0.5ZnxTixMn0.05Fe2.45−2xO4 ferrites (x=0.0 to 0.30 in steps of 0.05) +0.5wt% Bi2O3 prepared by a standard ceramic technique has been investigated. Electrical conductivity and dielectric measurements at different temperatures from 300 K to 700 K in the frequency range from 100 Hz to 2 MHz have been analysed. The variation of the real part of dielectric constant (ε′) and loss tangent (tanδ) with frequency and temperature has been studied; it follows the Maxwell–Wagner model based on the interfacial polarization in consonance with the Koops phenomenological theory. It is found that the permittivity of zinc and titanium substituted lithium ferrite improves and shows a maximum value (∼ 1.5×105) at 100 Hz for the x=0.25 sample. The dielectric transition temperature (Td) depends on the concentration of Ti and Zn in Li0.5ZnxTixMn0.05Fe2.45−2xO4. The saturation magnetization and Curie temperature both decrease with increase in the concentration of Ti and Zn in the ferrite

Permeability of Nb and Ta doped lithium ferrite in high frequency range

Nb and Ta doped lithium ferrites with composition of Li0.5Fe2.5O4 + xNb(2)O(5) and Li0.5Fe2.5O5 + xTa(2)O(5) (where x = 0, 0.3, 0.6, 0.9. 1.2 and 1.5 wt%) have been prepared by a solid-state reaction method. The effect of Nb2O5 and Ta2O5 on microstructure, magnetic properties like saturation magnetic moment (Ms), coercivity (Hc), retentivity (Mr) and permeability of lithium ferrite have been investigated in the frequency range 1 MHz to 1 GHz. The permeability of Nb2O5 doped lithium ferrite has been found higher (35) than pure lithium ferrite (25) at 1 MHz

Magnetic and magneto-transport properties of View the MathML source

The variation in structural, magnetic and magneto-transport properties of the double perovskite system (Ba0.8Sr0.2)2−xNdxFeMoO6 {0.0<X<0.5} induced by Nd3+ doping (electron doping) has been studied and compared. The samples were prepared by standard solid state reaction method in a reducing atmosphere. The parent compound showed a saturation magnetic moment value of 3.75 μB/f.u. at an applied field of 0.5 T and a change in magnetoresistance value up to 26% (77 K, 0.8 T). The Rietveld refinement of the X-ray diffraction data showed a continuous decrease in lattice parameters and Fe–Mo ordering with increasing Nd3+ doping. The Curie temperature was found to increase with Nd3+ doping (3 K per % of Nd) while the saturation magnetic moment values and magnetoresistance values were found to decrease. The observed variations in magnetic and magneto-transport properties of the system are explained on the basis of increasing antisite disorder defects and band filling effects induced by electron doping. We have observed the dominant role of band filling in determining the low field magnetoresistance of these systems

Magnetic properties of nano-crystalline Li0.35Cd0.3Fe2.35O4 ferrite prepared by modified citrate precursor method

Single phase nano-crystalline lithium cadmium ferrite Li0.35Cd0.3Fe2.35O4 is synthesized by a modified citrate gel precursor technique in different pH media. The modified citrate precursor technique reduces the formation of the impurity phase α-Fe2O3 in the inverse spinel phase of lithium ferrite. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the average crystallite size. As-prepared sample shows the paramagnetic behaviour of M–H curve measured by vibrating sample magnetometer (VSM). The coercivity (Hc) and magnetization (M) both increase with decrease in temperature from 300 K to 80 K. Temperature dependent magnetic properties below the Curie point are defined by the Bloch's law and Neel relaxation relations. The effect of annealing on magnetic properties at different temperature is studied