Thermophysical and Magnetic Properties of Magnetite – Polyethylene Composite

In this work, it is shown that the advantage of using matrix-stabilized magnetic nanoparticles to obtain polymer nanocomposites based on them is that such nanoparticles retain their dispersion and stability of size and shape in the technological modes of obtaining polymer nanocomposite materials, and thus ensured stable ferro- and superparamagnetic properties of the obtained target products. For the production of films by the method of hot pressing from blanks obtained in an injection molding machine or a mechanochemical mixture, a manual electrically heated hydraulic press was used. The magnetic properties of nanocomposite samples (about 50 mg on average) were studied using a vibration magnetometer. The character of the dependence of the magnetization on the magnitude of the magnetic field confirms the ferromagnetic character of the behavior of the obtained nanocomposites. The resulting film nanocomposites exhibit ferromagnetic properties at room temperature.

Numerical Investigation of the Stability and Spintronic Properties of Selected Quaternary Alloys

The use of electronic charge and spins (spintronics) has been proposed for much better data storage. This class of material is believed to have excellent capability for data integrity, low dynamic power consumption and high-density storage that showcases excellent protection against data loss. The spintronic and related properties have been investigated on four newly proposed quaternary alloys (NbRhGeCo, NbRhGeCr, NbRhGeFe and NbRhGeNi) through the first-principles calculation method of the Density Functional Theory (DFT). Specifically, the phonon frequencies, elastic stabilities, and the electronic structure were systematically studied in the full Heusler structure. The results predict that NbRhGeFe and NbRhGeCr are elastically and structurally stable. Both NbRhGeFe and NbRhGeCo are half-metals with ferromagnetic character, but NbRhGeCo is unfortunately elastically unstable. NbRhGeCr and NbRhGeNi are non-magnetic metallic alloys in their spin channels. All the results predict NbRhGeFe to be the only suitable among all the four alloys for spintronic application.

A study of micro structural, magnetic and electrical properties of La-Co-Sm nanoferrites (LCSF) synthesized by sol-gel method

A Lanthanum (La3+) doped Samarium-Cobalt nanoferrites (La_x,Co_0.2,Sm_0.2,Fe_(2-x) O_4, where x=0.0,0.5,1.0) have been synthesized by sol-gel method in citrate media. Obtained spinal ferrites micro structure properties have been investigated by XRD, FTIR, SEM-EDX, and TEM-SAED techniques. All the samples are nano in size with significant hysteresis. Micro structural analysis by XRD confirms the obtained samples showing the single phase cubic spinal structures with an average crystal size found from 12 nm to 25 nm, while the average particles sizes identified from TEM analysis are ranging from 21.5nm-26.8 nm (~23.4nm) and from 20.5 nm to 28(~26.4nm) nm for x=0.5,1.0. The lattice parameter found to be a= 8.402, 8.423, 8.467Å for the respective values of x= 0.0, 0.05, and 1.0. Electrical properties show increase in dc resistivity with increase in La3+ ion concentration. Finally, it was concluded that the doping of Lanthanum ion (La3+) in the ferrites structure is found to influencing the structural and electrical properties without scarifying the ferromagnetic character.

Effect of Erbium doping on GaN electronic and optical properties: First-principles study

In this work, we studied the electronic and optical properties of [Formula: see text] with a concentration [Formula: see text]. Based on a first-principle calculation and using the FP-LAPW full-linearized augmented plane wave method, to see the doping phenomenon with Erbium (Er) [Formula: see text], we used the three approximations: local spin density approximation (LSDA), the LSDA[Formula: see text] with [Formula: see text] is the Hubbard potential and the Becke–Johnson modification (mBJ). Our results show that the values of the structural parameters increase with the substitution of Ga by the Erbium atom. The analysis of the electronic structures in this study shows that the Er-doped GaN has a semi-metallic ferromagnetic character with the LSDA and mBJ approximations and a semiconductor behavior when we apply the Hubbard potential [Formula: see text]. The real and imaginary part of the dielectric function, refractive index, and extinction coefficient are also calculated and presented in the photon energy range up to 14 eV. In the optical spectrum, the intensity of the absorption coefficient is observed in the imaginary part of both doped and undoped GaN in the ultraviolet regions.

First principles calculations of the electronic, optical and thermoelectric performance of RbZn1−x NixF3 (x = 0, 0.25, 0.5, 0.75 and 1) alloys

First principles investigations of the electronic, optical and thermoelectric performance of RbZn[Formula: see text]Ni[Formula: see text]F3 (x = 0, 0.25, 0.5, 0.75 and 1) alloys are calculated using spin polarized full-potential linear augmented plane wave method, as implemented in Wien2k code. These alloys are found to be stable, ductile and can be formed with ferromagnetic character. RbZn[Formula: see text]Ni[Formula: see text]F3 are found to be insulator alloys with bandgap energy of range 7.02–5.14 eV using the modified Becke–Johnson functional. This gap is decreasing with increasing the Ni concentration in the unit cell. The optical parameters are calculated in the energy range upto 35 eV. The calculated static refractive index values are found directly proportional with the higher concentration of Ni atoms in the alloys. The transport coefficients are calculated using BoltzTrap code. The hole assumes the main charge carriers of the present alloys with p-type-doping for RbZnF3 alloy and n-type-doping for RbZn[Formula: see text]Ni[Formula: see text]F3. The calculated optical and transport coefficient values show promising optoelectronic and thermoelectric applications of the studied alloys.

Increase of Curie temperature with La doping in the double perovskite Sr2-LayFeMoO6 within an electronic correlation approach

The double perovskite compound Sr2FeMoO6 has a half-metallic ferromagnetic character and ahigh Curie temperature (420 K). Fe-Mo usually present some degree of disorder in either Fe orMo ions, it is therefore fundamental to understand the role of electronic and structural parameterscontrolling the half-metallic character together with a Curie temperature as high as possible. We replaceddivalent Sr2+ by trivalent La3+ ions in Sr2FeMoO6 system to observe the Curie temperaturebehavior. We present an electronic approach using the Green's functions and the renormalizationperturbation expansion method, with localized Fe-spins and conduction Mo-electrons interactingwith the local spins via a double-exchange-type mechanism. We also include the electronic correlationsamong the conduction electrons within a mean-eld approximation. Our results showthe density of states and the Curie temperature behavior when La concentration increases for theSr2y-yLayFeMoO6 system

Supramolecular Hydrogen Bonded 3D Molecular Self Assembly Constructed from [(Co (nicotinamide)2(thiocyanate)2(H2O)2] Complex Showing Anti-ferromagnetic Character

A new three dimensional hydrogen bonded cobalt frame work from [Co(nicotinamide)2(thiocyanate)2(H2O)2] was synthesized and characterized by X-ray diffraction, magnetism ,TGA and IR spectroscopy. The compound crystallizes in Triclinic space group P-1 with a = 7.5475(19), b = 8.054(2), c =8.932(2). Alpha=73.347(4), beta=70.067(4), gamma=66.559(4) with space group P-1 Z = 1, 'C14 H16 N6 Co O4 S2', Mr =455.38, F(000) = 233 and μ(MoKα) =0.71073 mm-1. The final R = 0.0497 and wR = 0.1461 for 4185 observed reflections with I > 2σ(I) and R = 0.0721 and wR = 0.1619 for all data. X-ray diffraction analyses revealed that Co(1) is linked by the nicotinamide ligands to form the ladder shape along the c axis, which is further extended into two-dimensional networks via the joint of Co(2) along the a axis. Moreover, these two dimensional motifs are interconnected by the thiocyanate S...H bridges to form a complicated 3-D polymeric framework. The magnetic susceptibility data at 1000Oe external field in the temperature range 2-300 K obeys the Curie-Weiss law, giving θ = -24.12 K and C =2.43 thus indicating a dominant strong antiferromagnetic interaction and/or spin orbital coupling between the Co (II) ions.

Low Band Gap Co80Ni20@RGO Nanocomposite

We report a novel approach of designing ordered arrangement of disorder on the extended structures of graphene. We prepared single phase nanoparticles of Co80Ni20 alloy embedded in Reduced Graphene Oxide (RGO). Co80Ni20 shows a large moment and a soft ferromagnetic character like permalloy at room temperature. Temperature dependence of permittivity shows a behavior quite contrary to usual ceramic materials showing an increase with decreasing temperature, exhibiting a maximum. A very large magnitude of permittivity ~ 5000 is observed, which is possibly related to an interesting Maxwell-Wagner type effect arising from the charge localization in the graphene sheets. For a deeper insight of the mechanism, correlations with other phenomena are studied through magnetization, dc resistivity, I-V etc. investigations. Temperature dependent magnetization indicates toward strong ferromagnetic interaction and MH loop shows low coercivity ferromagnetic interaction at 4 K and even at room temperature.