Ferromagnetism from Acceptors of Native Point Defects in (Zn, Mn)O Doped Systems

In this paper, we represent a theoretical study of the (Zn, Mn)O doped system with native point defects of ZnO as oxygen interstitials (O_i) and zinc vacancies (V_Zn). Under these defects, it has been shown that the ground state can be converted from spin glass to ferromagnetic phase, by performing ab initio density functional theory calculations relying on the Korringa?CKohn?CRostoker coherent potential approximation (KKR-CPA) method employing the local density approximation (LDA) with the parameterization by Morruzi, Janak, and Williams. The stability of magnetism in the (Zn, Mn)O doped system with different native point defects has been discussed. We find that acceptor-like defects (that is, O_i, O_Zn, and V_Zn) may cause the enhancement of the ferromagnetic characteristics in ZnMnO with increasing T _c . Based on the theoretical results, we suggest that the native point defects have a key role with respects to the FM properties. Using the mean field approximation, the Curie temperature in our studied model is estimated.     

Ferromagnetism and Anti-ferromagnetism in Nano-films with Alternate Crystal Fields: Monte Carlo Study

Using Monte Carlo simulations, the magnetic properties of the Ising model based on a nano-film formed by alternating layers are studied. The effect of a reduced crystal field with the anti-ferromagnetic and ferromagnetic reduced exchange interactions is deduced for fixed system sizes: N= 9 and 10 layers. Indeed, the anti-ferromagnetic reduced exchange interaction increases when one increases of the number layers, for odd or even values of N. The total magnetization increases with increasing of the anti-ferromagnetic and the ferromagnetic reduced exchange interactions. It is found that the total magnetization remains almost constant for large values of layer numbers (N).     

Physicochemical Characteristics,Nutritional Properties,and Health Benefits of Argan Oil: A Review

The argan tree (Argania spinosa L. Skeels), an endemic tree in Morocco, is the most remarkable species in North Africa, due to its botanical and bioecologic interest as well as its social value. Argan oil is traditionally well known for its cardioprotective properties and it is also used in the treatment of skin infections. This paper gives an overview of scientific literature available on nutritional and pharmacologic properties of argan oil. Owing to its unique organoleptic properties associated with its cardioprotective properties, argan oil has found, recently, its place in the highly competitive international edible oil market. This success is a very positive sign for the preservation of the argan tree, the argan forests and, therefore, in general, the biodiversity.     

First-principles prediction of the magnetism of 4f rare-earth-metal-doped wurtzite zinc oxide

Electronic structure and magnetic properties of wurtzite ZnO semiconductor doped with rare earth （RE=La, Ce, Pr, Pm, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb） atoms were studied using spin-polarized density functional theory based on the full-potential linear augmented plane wave （FP-LAPW） method as implemented in the Wien2k code. In this approach the generalized gradient approximation （GGA） was used for the exchange-correlation （XC） potential. Our results showed that the substitution of RE ions in ZnO induced spins polarized localized states in the band gap. Moreover, the studied DMSs compounds retained half metallicity at dopant concentration x=0.625%for most of the studied elements, with 100%spin polarization at the Fermi level （EF）. The total magnetic moments of these compounds existed due to RE 4f states present at EF, while small induced magnetic moments existed on other non-magnetic atoms as well. Finally, the energy difference between far and near configurations was investigated. It was found that the room temperature ferromagnetism was possible for RE-doped ZnO at near configuration. Since the RE-RE separation was long enough （far configuration） for magnetic coupling, the system became paramagnetic or antiferromagnetic ground state.     

Triviality and Dimension of a System of Algebraic Differential Equations

We present an algorithm that tests the triviality and computes the differential dimension and a parametric set for an ordinary differential polynomial ideal. No factorization is needed. The basic operation in our algorithm is the test of invertibility of an algebraic polynomial with respect to a finite set of algebraic polynomials. The algorithm has been implemented in the computer algebra system MAPLE and has been tested successfully on many examples.     

Visual force sensing with flexible nanowire buckling springs

A calibrated method of force sensing is demonstrated in which the buckled shape of a long flexible metallic nanowire, referred to as a 'nanoneedle', is interpreted to determine the applied force. An individual needle of 157?nm diameter by 15.6?μm length is grown on an atomic force microscope (AFM) cantilever with a desired orientation (by the method of Yazdanpanah et al 2005 J. Appl. Phys. 98 073510). Using a nanomanipulator the needle is buckled in the chamber of a scanning electron microscope (SEM) and the buckled shapes are recorded in SEM images. Force is determined as a function of deflection for an assumed elastic modulus by fitting the shapes using the generalized elastica model (De Bona and Zelenika 1997 Proc. Inst. Mech. Eng. C 211 509-17). In this calibration the elastic modulus (68.3?GPa) was determined using an auxiliary AFM measurement, with the needle in the same orientation as in the SEM. Following this calibration the needle was used as a sensor in a different orientation than the AFM coordinates to deflect a suspended PLLA polymer fiber from which the elastic modulus (2.96?GPa) was determined. The practical value of the sensing method does depend on the reliability and ruggedness of the needle. In this study the same needle remained rigidly secured to the AFM cantilever throughout the entire SEM/AFM calibration procedure and the characterization of the nanofiber.     

Improved Power Conversion Efficiency with Tunable Electronic Structures of the Cation-Engineered [Ai]PbI3 Perovskites for Solar Cells: First-Principles Calculations

Higher power conversion efficiencies for photovoltaic devices can be achieved through simple and low production cost processing of APbI3(A=CH3NH3,CHN2H4,…) perovskites. Due to their limited long-term stability, however, there is an urgent need to find alternative structural combinations for this family of materials. In this study, we propose to investigate the prospects of cation-substitution within the A-site of the APbI3 perovskite by selecting nine substituting organic and inorganic cations to enhance the stability of the material. The tolerance and the octahedral factors are calculated and reported as two of the most critical geometrical features, in order to assess which perovskite compounds can be experimentally designed. Our results showed an improvement in the thermal stability of the organic cation substitutions in contrast to the inorganic cations, with an increase in the power conversion efficiency of the Hydroxyl-ammonium (NH₃OH) substitute to η = 25.84%.     

Study on Solid Acid Catalyzed Hydrolysis of Maltose and Related Polysaccharides

Within a study on combined hydrolysis and oxidation of starch toward D -gluconic acid the solid acid catalyzed hydrolysis of maltose as model compound was investigated. Acid zeolites and ion-exchange resins in the H*-form as well as amorphous silica-aluminas were used as the catalysts. The optimal conditions found for maltose were applied in the hydrolysis of amylose and starch. It is shown that the catalysis by zeolites and alumino-silicates involves homogeneous as well as heterogeneous catalysis.