161 research outputs found
The Ferromagnetic and half metallic behaviors of Fe- and Co- doped SnO2 within Local Density Approximation and Self-Interaction-Corrected
Using ab-initio calculation based on the Korringa-Kohn-Rostoker Coherent Potential Approximation (KKR-CPA) method in connection with the local density approximation without and within self-interaction-corrected (LDA and LDA-SIC), we represent a theoretical study of the SnO2 doped system with transition metals (TM) which are Iron (Fe) and Cobalt (Co). In this system, the stability of the ferromagnetic state compared with the spin-glass state is investigated by comparing their total energies. The Ferromagnetic and half metallic behaviors was observed and conformed with the local-moment-disordered (LMD) state energy for LDA (local density approximation) and LDA-SIC (local density approximation-self-interaction correction) approximation in [Sn0.95TM0.05(Fe or Co)]O2 . Based on mean field method, the Curie temperature is estimated. To explain the origin of magnetic behavior, we give information about total and atom projected density of states functions of Fe and Co elements and we propose a model which describes magnetic interaction in [Sn0.95TM0.05(Fe or Co)]O2
Engineering the magnetic and magnetocaloric properties of PrVO3 epitaxial oxide thin films by strain effects
Combining multiple degrees of freedom in strongly-correlated materials such
as transition-metal oxides would lead to fascinating magnetic and
magnetocaloric features. Herein, the strain effects are used to markedly tailor
the magnetic and magnetocaloric properties of PrVO3 thin films. The selection
of appropriate thickness and substrate enables us to dramatically decrease the
coercive magnetic field from 2.4 T previously observed in sintered PVO3 bulk to
0.05 T for compressive thin films making from the PrVO3 compound a nearly soft
magnet. This is associated with a marked enhancement of the magnetic moment and
the magnetocaloric effect that reach unusual maximum values of roughly 4.86 uB
and 56.8 J/kg K in the magnetic field change of 6 T applied in the sample plane
at the cryogenic temperature range (3 K), respectively. This work strongly
suggests that taking advantage of different degrees of freedom and the
exploitation of multiple instabilities in a nanoscale regime is a promising
strategy for unveiling unexpected phases accompanied by a large magnetocaloric
effect in oxides.Comment: This paper is accepted for publication in Applied Physics Letter
Monte Carlo simulation of magnetic phase transitions in Mn doped ZnO
The magnetic properties of Mn-doped ZnO semi-conductor have been investigated
using the Monte Carlo method within the Ising model. The temperature
dependences of the spontaneous magnetization, specific heat and magnetic
susceptibility have been constructed for different concentrations of magnetic
dopant Mn and different carrier concentrations. The exact values of Mn
concentration and carrier concentration at which high temperature transition
occurs are determined. An alternative for the explanation of some controversies
concerning the existence and the nature of magnetism in Mn diluted in ZnO
systems is given. Other features are also studied.Comment: 10 pages, 9 figures, To appear in Journal of Magnetism and Magnetic
Material
An easy route to synthesis black phosphorus at low pressure and soft conditions
Black phosphorus a promising candidate for large application, due to his variety of structural and physical properties, can be prepared by a very low-coast reaction route with high purity and crystallinity. Black phosphorus is prepared from red phosphorus at 873K under reduced pressure using a simple and low cost catalytic system. The quality of crystal with lattice parameters a=3.31Å, b=10.48Å, c=4.37Å can be approved by a series of characterizations like
scanning microscopy electron (SEM), energy dispersive spectrometry (EDX), Raman spectroscopy and powder X-rays. The new preparation method of black phosphorus represents an easy, effective and low cost approach to avoid complicated preparative setups, toxic catalysts, or “dirty” flux methods and is of general interest in elemental chemistry
Structural and Magnetic Properties of Nanosized strontium Hexaferrite Powders: Experimental and theoretical investigation
Strontium M-type hexagonal ferrites were synthesized at different calcination temperatures (800 °C, 1000°C and 1100 °C) using sol-gel autocombustion method. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Mössbauer spectroscopy (MS) and superconducting quantum interference device magnetometer (SQUID) techniques were used to characterize crystal structure, phase composition, morphology and magnetic properties. TGA gives T=800 °C as beginning of suitable calcination. Hexaferrite structure of single phase is obtained according to XRD results for all samples with crystallite size between 28 nm and 35 nm. SEM images show the growth of grain size with increasing of annealing temperature. (BH)max is calculated based on SQUID results and shows an enhancement between T=800°C and T= 1000°C of 25%. The magnetic properties observed at low temperature are explained and confirmed by ab-initio calculations
Energy product and magnetic properties of strontium hexagonal ferrite: experimental and theoretical investigation
The interest toward hard magnetic materials increases in the last years. In order to have the best magnetic properties of these materials, researchers count on the efficiency of different
synthesis methods.
In permanent magnets application, ferrite materials possess a good place among the other magnet families. In permanent magnets field, the more important parameter that describes the magnetic strength of a magnet is the maximum energy product (BH)max. A strong permanent magnet has an important value of (BH)max.
In this work, we will study the effect of annealing temperature on maximum energy product
and other magnetic properties of Strontium hexaferrite SrFe12O19 synthesized using sol-gel autocombustion method, with different annealing temperatures, characterized using Thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Mössbauer spectroscopy (MS) and superconducting quantum interference device magnetometer (SQUID). Ab initio calculation for magnetic properties is also performed in order to compare it with low temperature experimental results
Electronic and optoelectronic properties of black phosphorous
Herein, we present the enormous capabilities of the most recent rediscovered 2D material named black phosphorous (BP). It offers a solution for several technological limitations that appears in conventional 2D materials such as transition metal dichalcogenides/oxides etc. In the present work, we have demonstrated the electronic and optoelectronic properties of BP via realizing field effect transistors.
Investigation of the electronic, magnetic, exchange interactions, and magnetocaloric properties in orthotitanate oxides RTiO3 (R = Er, Ho)
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