SPIN

Quantum tunneling of the magnetization (QTM) of the spin-1/2 Vanadium-15 (V${}_{15})$ single molecular magnets (SMMs) is investigated by means of the effective field theory developed by Kaneyoshi. We deal with the two hexagon layers (shell, V${}_S)$ and one triangular interlayer (core, V${}_C)$ with the spin-1/2 Ising particles. We find that the V${}_{15}$ has a normal ferromagnetic hysteresis behavior for its all spins are up (parallel). However, V${}_{15}$ has a staircase-like hysteresis behavior that is the signature of the QTM for the spin-down orientation (antiparallel) of the core. QTM appears with the splitting of the magnetizations versus temperature ($M$–$T)$ and external field ($M$–$H)$ curves. Namely, QTM occurs from $+m_{\mathrm{\text{VC}}1}$ to $-m_{\mathrm{\text{VC}}2}(|m_{\mathrm{\text{VC}}1}|>|m_{\mathrm{\text{VC}}2}|)$ in the core, from +$m_{\mathrm{\text{VS}}1}$ to $+m_{\mathrm{\text{VS}}2}$ $(|m_{\mathrm{\text{VS}}1}|>|m_{\mathrm{\text{VS}}2}|)$ in the shell (only $m_{\mathrm{\text{VS}}}$–$H$ curves at $T>$ 0.1) and from $+M{1}_{V15}$ to $+M{2}_{V15}$ $(|M{1}_{V15}|>|M{2}_{V15}|)$ in the total V${}_{15}$. By considering these different splitting behaviors of the magnetizations of the shell, core and total $V_{15}$ at $T<T_C$ and $T>T_C$, we suggest three different kinds of QTM: 1-ferromagnetic QTM (FMQTM) at $T<T_C$ for the shell, 2-antiferromagnetic QTM (AFMQTM) at $T<T_C$ for the core and 3-paramagnetic QTM (PMQTM) at $T>T_C$ for the shell, core and total V${}_{15}$ SMM. Moreover, it is found that there is a relationship between the QTM and type II and surface superconductivity. The EFT results of QTM in V${}_{15}$ are in good agreement with the other theoretical and experimental results of the V${}_{15}$ and other SMMs.

The structural electronic and magnetic properties of the double perovskite Ca₂CrNbO₆ in the cubic structure are investigated using the empirical full-potential linearized augmented plane wave (FP-LAPW) method within the framework of the spin-polarized density functional theory (DFT). These properties are calculated using the Generalized Gradient Approximation (GGA), $\mathrm{\text{GGA}}+U$ and modified Becke–Johnson mBJ-GGA. In addition, the real and imaginary parts of the optical dielectric function and the reflectivity, and the refractive spectra are computed and the main features shown by their spectra are ascertained on the base of the investigation of density of states.

In this work, Monte Carlo simulations have been performed to investigate the magnetic properties and thermal behavior of different Husimi-like structures: triangular, square and pentagonal. In fact, the Blume-Capel model has been adopted to study such Husimi lattices in the framework of the Ising model spin-1. Furthermore, we have examined the computed blocking temperatures. Also, the behavior of each Husimi geometry has been studied and discussed. Besides, the effects of the magnetization versus the crystal field, the exchange coupling interaction and the external magnetic field have been investigated. Such comparison of triangular, square and pentagonal Husimi-like structures allowed us to deduce interesting properties related to the geometry of each structure.

In this work, we investigate the scattering phenomena at the inhomogeneous boundary of a magnetic interface in two-dimensional (2D)-triangular ferromagnetic waveguide. We especially examine two ferromagnetic interfaces, named heavy and superheavy solitons in 2D-triangular lattices. The system is supported on a nonmagnetic substrate. Therefore, each spin site in the lattice can be considered free from magnetic interactions with its environment. The spin excitations in the modeled system are studied by the field matching theory (FMT). Their magnons transmission/reflection, localized spin states as well as the local density of spin states (LDOS) are calculated and analyzed. They are derived as elements of a Landauer type scattering matrix. The magnonic spectra are calculated specifically for two distinct interfaces, which join the two semi-infinite perfect 2D-triangular waveguides. The inter-atomic magnetic exchange is varied on the interface domain to investigate the consequences of magnetic softening and hardening for the calculated magnetic properties. The numerical results show the interference effects between the incident magnons and the localized spin states on the interface domain, with characteristic magnetic resonances that vary according to each configuration. The numerical results yield an understanding for the relation between the coherent magnon propagation and the interface configuration in the perfect 2D-triangular system.

Thermoelectric properties of superlattice magnetic tunnel junctions (SL-MTJs) comprising of MgO barriers, ZnO quantum wells and CoFeB contacts are investigated in the linear and nonlinear response regime. The transmission function is calculated by the nonequilibrium Green’s function (NEGF) formalism. The anti-reflective (AR) regions idea in SL-MTJs leads to an enhancement in power factor as well as output power due to the presence of “box-car” transmission in AR-MTJs. Therefore, it can be proposed as a new way to progress in the field of spincaloritronics.

In this paper, we present an ab initio study, based on the density functional theory (DFT) approach and GGA-PBE approximation, of the structural, electronic and magnetic properties of new quaternary Heusler compounds LiX${}^{\prime }$NO (${\mathrm{\text{X}}}^{\prime }=\mathrm{\text{Ba}}$, Ca and Sr). We searched the structural stability of these quaternary Heusler among three different atomic arrangements (type-1, type-2 and type-3) by calculating of the cohesive energy, elastic constant and phonon dispersion. We found that the type-2 structure is the most stable structure in the ferromagnetic phase. The results of the magnetic and electronic properties show that the LiX${}^{\prime }$NO quaternary compound exhibits a half-metallic character with 100% spin polarization at the Fermi level and obey the Slater Pauling rule. It is also divulged that half-metallicity comes mainly from N and O atoms. These theoretical results make these new quaternary alloys as very promising materials for spintronic device.

The structural, electronic, elastic and magnetic properties of CoCrScIn were investigated using first principle calculations with applying the full-potential linearized augmented plane waves (FP-LAPW) method, based totally on the density functional theory (DFT). After evaluating the results, the calculated structural parameters reveal that CoCrScIn compound is stable in its ferrimagnetic configuration of the type-III structure. The mechanical properties show its brittle and stiffer behavior. The formation energy value showed that CoCrScIn can be experimentally synthesized. Additionally, the obtained band structures and density of states (DOS) reflect the half-metallic behavior of CoCrScIn, with an indirect bandgap of 0.43eV. The total magnetic moment of 3${\mu }_B$ and half-metallic ferrimagnetic state are maintained in the range 5.73–6,79 Å. The magnetic moment especially issues from the Cr-$d$ and Co-$d$ spin-polarizations. Furthermore, the calculations of Curie temperature reveal that CoCrScIn has high magnetic transition temperature of 836.7K.

A novel lead zinc titanate tungsten oxide (PbZn${}_{1∕3}$Ti${}_{1∕3}$W${}_{1∕3}$O${}_3)$ single perovskite was synthesized employing a cost-effective solid-state reaction technique. A phase transition occurs from tetragonal (P4mm) to monoclinic (C2/m) after substituting zinc (Zn) and tungsten (W) into the B-site of the pure lead titanate. The average crystallite size and micro-lattice strain are 66.2nm and 0.159%, respectively, calculated by the Williamson–Hall method. The grains are uniformly distributed through well-defined grain boundaries and the average grain size is about 17.8$\mu$m analyzed from the SEM micrograph. Raman spectrum suggests the presence of all constituent elements in the sample. The UV–Visible study suggests that the sample is suitable for photovoltaic applications because of high bandgap energy $E_g=4.17$eV. The dielectric study confirms the negative temperature coefficient resistance (NTCR) behavior of the sample. The activation energy increases from 13.9meV to 142meV with a rise of temperature suggesting that ac conductivity is thermally activated. The thermally activated relaxation process was managed by immobile charge carriers at low temperatures while defects and oxygen vacancies at higher temperatures. The presence of the asymmetrical curves in modulus plots confirms the non-Debye-type behavior. Both Nyquist and Cole–Cole semi-circular arcs confirm the semiconductor nature of the sample.