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.     

Electronic Structure and Magnetic Properties of Zinc-Blende Co-Doped GaN with N Vacancies

The electronic structure and magnetic properties of zinc-blende structure of (Ga,Co)N phase with N vacancy defects are investigated using the Korringa–Kohn–Rostoker (KKR) method combined with coherent potential approximation (CPA). The results show that (Ga,Co)N phase is ferromagnetically polarized with an enhancement of the polarization and that the electronic structure can be modified simply by changing the concentration of N vacancies. Moreover, the (Ga,Co)N with high density of N vacancies shows a drastic increase of the magnetic moment of cobalt in the parent GaN compound, to reach a maximum value of 1.7 μ_B/Co at 8 at.%, which is in good agreement with the experimental values reported in the literature.     

Decomposition of tangerine and pomegranate wastes in water and soil: characterisation of physicochemical parameters and global microbial activities under laboratory conditions

In most scientific research, interest is given to heterogeneous green household waste collected from landfills. This paper reports a study of the enzymatic dynamics of green household waste separately decomposed in water and soil. The study showed that the highest dehydrogenase activity (800.53 μg of TFP[tri phenyl formazan]/hr/gdw) was noted for the digested pomegranate waste in the soil. The overall hydrolytic activity (0.12 μmol of hydrolysed FDA[fluorescein di acetate]/hr/gdw), and the carbon dioxide (CO₂) release were higher (777.20 μg of CO₂/hr/gdw) in digestion in water. For tangerine waste digested in water, the CO₂ release (918.96 µg of CO₂/hr/gdw) and overall hydrolytic activity (0.19 μmol of hydrolysed FDA/hr/gdw) were most pronounced. The values of physicochemical parameters were generally lower in tangerine waste than in pomegranate waste, and lower in water decomposition than in soil decomposition.     

Physical Proprieties of Ferrites Nanoparticles

Synthesis optical and magnetic of nearly monodisperse Fe₃O₄ nanoparticles through a simple coprecipitation method was studied in this work, Well-defined disperse nanospheres with an average size of 10 nm have been synthesized without any surfactant. Structural optical and magnetic properties were investigated by means of X-ray diffraction, transmission electron microscopy (TEM), UV-visible measurement, and superconducting quantum interference device (SQUID). The critical and blocking temperature, saturation magnetization, magnetic remanence, and coercive field of Fe₃O₄ nanoparticles are obtained at room temperature.     

Carbohydrate‐based polyurethanes: A comparative study of polymers made from isosorbide and 1,4‐butanediol

A set of linear polyurethanes containing isosorbide units were synthesized by polymerization in solution from HDI and MDI diisocyanates and 1,4‐butanediol (BD), isosorbide (Is) or diisosorbide diurethanes (Is₂HDI and Is₂MDI) as diols. The thermal transitions, thermal stability, and crystal structure of the polyurethane homopolymers and copolymers containing isosorbide were evaluated and compared with those displayed by their polyurethane analogues entirely made of BD. It was found that incorporation of Is units in the polyurethane chain produced significant changes in T_g, T_m, and T_d but no significant differences were noticed between copolymers made from Is or Is₂ monomers. Degradation assays revealed that the presence of Is units increased slightly the hydrolysis rate of polyurethanes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Magnetic Properties of Zn0.8(Fe0.1,Co0.1)O Diluted Magnetic Semiconductors: Experimental and Theoretical Investigation

Structural and magnetic properties of Zn_0.8(Fe_0.1, Co_0.1)O bulk diluted magnetic semiconductor have been investigated using X-ray diffraction (XRD) and magnetic measurements. TEM (Transmission Electron Microscopy) images confirmed the high crystallinity and grain size of Zn_0.8(Fe_0.1,Co_0.1)O powder, the samples were characterized by energy dispersive spectroscopy (EDS) to confirm the expected stoichiometry. This sample has been synthesized by co-precipitation route. The study of magnetization hysteresis loop measurements infers that the bulk sample of Zn_0.8(Fe_0.1,Co_0.1)O shows a well-defined hysteresis loop at T _c (200?K) temperature, which reflects its ferromagnetic behavior. Hydrogenation treatment was used for the control of phase separation. Based on first-principles spin-density functional calculations, using the Korringa?CKohn?CRostoker method (KKR) combined with the coherent potential approximation (CPA), the ferromagnetic state energy was calculated and compared with the local-moment-disordered (LMD) state energy. The mechanism of hybridization and interaction between magnetic ions in Zn_0.8(Fe_0.1,Co_0.1)O is also investigated.     

Study of Magnetic Properties in Spinels Co x Zn1?x Cr2O4 systems

The exchange interactions J _AA(x) and J _AB(x) are calculated by using a probability law for the Co _x Zn_1?x Cr₂O₄. The magnetic properties of a diluted ferromagnetic spinels Co _x Zn_1?x Cr₂O₄ system are investigated by using the high-temperature series expansions combined with the Padé approximants. The magnetic phase diagram, i.e., T _N versus?x, and the critical exponent associated with the magnetic susceptibility (??) are deduced.     

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.