arXiv subjects

M. Mokhtari

Publications and source records attributed to M. Mokhtari.

8 recordsLinked to original sources

arXiv2021

First-principles investigation of half-metallic ferromagnetism of Fe$_2$YSn (Y = Mn, Ti and V) Heusler alloys

In this paper, we use the first-principles calculations based on the density functional theory to investigate structural, electronic and magnetic properties of Fe$_{2}$YSn with (Y = Mn, Ti and V). The generalized gradient approximation (GGA) method is used for calculations. The Cu$_{2}$MnAl type structure is energetically more stable than the Hg$_{2}$CuTi type structure. The negative formation energy is shown as the evidence of thermodynamic stability of the alloy. The calculated total spin moment is found as 3$μ_\text{B}$ and 0$μ_\text{B}$ at the equilibrium lattice constant for Fe$_{2}$MnSn and Fe$_{2}$TiSn respectively, which agrees with the Slater-Pauling rule of $M_t= Z_t-24$. The study of electronic and magnetic properties proves that Fe$_{2}$MnSn and Fe$_{2}$TiSn full-Heusler alloys are complete half-metallic ferromagnetic materials.

cond-mat.mtrl-sci↗

arXiv2021

Prediction of electronic and half metallic properties of Mn$_2$YSn (Y = Mo, Nb, Zr) Heusler alloys

We investigate the structural, electronic and magnetic properties of the full Heusler compounds Mn$_2$YSn (Y = Mo, Nb, Zr) by first-principles density functional theory using the generalized gradient approximation. It is found that the calculated lattice constants are in good agreement with the theoretical values. We observe that the Cu$_2$MnAl-type structure is more stable than the Hg$_2$CuTi type. The calculated total magnetic moments of Mn$_2$NbSn and Mn$_2$ZrSn are 1 $μ_{\text{B}}$ and 2 $μ_{\text{B}}$ at the equilibrium lattice constant of 6.18 Åand 6.31 Å, respectively, for the Cu$_2$MnAl-type structure. Mn$_2$MoSn have a metallic character in both Hg$_2$CuTi and Cu$_2$MnAl type structures. The total spin magnetic moment obeys the Slater-Pauling rule. Half-metal exhibits 100% spin polarization at the Fermi level. Thus, these alloys are promising magnetic candidates in spintronic devices.

cond-mat.mtrl-sci↗

arXiv2021

Ab initio study of structural, electronic and magnetic properties of XSn$_3$ (X = Gd, Cm) and Gd$_x$Cm$_{1-x}$Sn$_3$ compounds

In this paper, the structural, electronic and magnetic properties of the GdSn$_3$, CmSn$_3$ and Gd$_x$Cm$_{1-x}$Sn$_3$ compounds ($x = 0.25$, $0.5$ and $0.75$) were studied using the full-potential linearized augmented plane wave method, within the generalized gradient approximation$+U$. The ground-state properties are determined for the bulk materials GdSn$_3$, CmSn$_3$ and Gd$_x$Cm$_{1-x}$Sn$_3$ crystallized in AuCu$_3$-type structure. The calculated structural, electronic and magnetic properties of GdSn$_3$ compound are in good agreement with the existing experimental and theoretical data. It is found that the most stable magnetic configurations of both compounds CmSn$_3$ and GdSn$_3$ are anti-ferromagnetic type A (AFM-A) and have a metallic behavior. The magnetic moment found decreases with increasing the Cm composition in Gd$_x$Cm$_{1-x}$Sn$_3$ compounds. The results show that the GdSn$_3$, CmSn$_3$ and Gd$_x$Cm$_{1-x}$Sn$_3$ compounds share some properties, and may well be useful for spintronic applications.

cond-mat.mtrl-sci↗

arXiv2020

Theoretical study of phase stability, electronic and magnetic properties of Rh$_2$CrGe$_{1-x}$Al$_x$ ($x = 0$, $0.25$, $0.50$, $0.75$ and $1$) Heusler alloys by FP-LAPW method

First-principle calculations were performed within the framework of the density functional theory (DFT) using FP-LAPW method as implemented in WIEN2k code to determine the structural stability, electronic and magnetic properties of Rh$_2$CrGe$_{1-x}$Al$_x $($x = 0$, $0.25$, $0.50$, $0.75$ and $1$). The results showed that for Rh$_2$CrAl and Rh$_2$CrGe, the Cu$_2$MnAl-type structure is energetically more stable than Hg$_2$CuTi-type structure at the equilibrium volume. The calculated densities of states for Rh$_2$CrAl and Rh$_2$CrGe show half-metallic and nearly half-metallic behavior, respectively. Rh$_2$CrGe$_{1-x}$Al$_x$ ($x = 0.25$, $0.50$, $0.75$) these alloys show a half-metallic character, and these compounds are predicted to be good candidates for spintronic applications.

cond-mat.mtrl-sci↗

arXiv2019

Dynamics of disease spread. Effect of the characteristic times

Dynamic properties of spreading infection through a heterogeneous population are studied numerically and analytically using a dynamic variant of Watts and Strogatz Small World Network-based stochastic Susceptible-Exposed-Infectious-Removed (SEIR) epidemic model. This model includes the main realistic parameters usually characterizing transmissible diseases, such as the force of infection, latency and infection times. As far as the latency time remains smaller than that of infection, the proportion of infected individuals increases exponentially with time, otherwise an oscillatory behavior appears. This may explain the periodic behaviors in time observed by the health prevention services. It is also shown that periodic epidemiological surveys overestimate or underestimate the dynamics of infection if the survey periods do not exactly correspond to the characteristic times of the infection. Further discussion is provided on the diffusion and relaxation processes involved in this model, and their relation to the infection characteristic time.

q-bio.PE↗

arXiv2018

Theoretical study of the structural stability, electronic and magnetic properties of XVSb (X $=$ Fe, Ni, and Co) half-Heusler compounds

The structural, electronic and magnetic properties of half-Heusler compounds XVSb (X $=$ Fe, Co and Ni) are investigated by using the density functional theory with generalized gradient approximation (GGA), and Tran-Blaha modified Becke-Johnson (TB-mBJ) exchange potential approximation. It is found that the half-metallic gaps are generally reasonably widened by mBJ as compared to the GGA approximation. The magnetic proprieties of XVSb (X $=$ Fe, Co and Ni) are well defined within mBJ with an exact integer value of magnetic moment. The band gaps given by TB-mBJ are in good agreement with the available theoretical data. The FeVSb exhibits a semiconductor nature. The CoVSb and NiVSb present half-metallic behaviour with total magnetic moment of $1μ_\text{B}$ and $2μ_\text{B}$ in good agreement with Slater-Pauling rule. These alloys seem to be a potential candidate of spintronic devices.

cond-mat.mtrl-sci↗

arXiv2016

Effect of film thickness on the width of percolation threshold in metal-dielectric composites

The effect of thickness on the width of the percolation threshold in metal-dielectric composite films was examined. The distribution of current intensities through cubic networks of metal and dielectric components was determined using Kirchhoff's equations. From the tail of current distribution, the width of the percolation threshold was defined using Lévy statistics, and determined as a function of the film thickness for a system size 100. In the 2D-3D crossover region, the percolation width decreases as a power-law with a power exponent of $ 0.36\pm 0.01$.

cond-mat.stat-mech↗

arXiv2005

Dynamics of the Markov Time Scale of Seismic Activity May Provide a Short-Term Alert for Earthquakes

We propose a novel method for analyzing precursory seismic data before an earthquake that treats them as a Markov process and distinguishes the background noise from real fluctuations due to an earthquake. A short time (on the order of several hours) before an earthquake the Markov time scale $t_M$ increases sharply, hence providing an alarm for an impending earthquake. To distinguish a false alarm from a reliable one, we compute a second quantity, $T_1$, based on the concept of extended self-similarity of the data. $T_1$ also changes strongly before an earthquake occurs. An alarm is accepted if {\it both} $t_M$ and $T_1$ indicate it {\it simultaneously}. Calibrating the method with the data for one region provides a tool for predicting an impending earthquake within that region. Our analysis of the data for a large number of earthquakes indicate an essentially zero rate of failure for the method.

physics.geo-ph↗