Giant magnetocapacitance effect in nickel zinc ferrite impregnated mesoporous silica

Mesoporous silica with a pore diameter of around 5 nm was synthesized by a solution technique. Nickel zinc ferrite (NZF) phase was grown within these nanochannels. The dielectric permittivity showed dispersion as a function of frequency characteristic of a Maxwell–Wagner capacitor. The nanocomposite exhibited a large magneto-capacitance coefficient of 44% at room temperature at an applied magnetic field of 1.5 T. The dielectric loss of the nanocomposite was fairly low (~ 0.01). The present strategy of composite synthesis will lead to the preparation of materials having large values of magneto-capacitive coefficients for device applications

Anion mediated diversity in the nuclearity of nickel(II) complexes with a N2O donor Schiff base: Formation of a supra-molecular chain via Br center dot center dot center dot Br interactions

Two nickel(II) complexes, [Ni(L)(2)] (1) and [Ni-2(mu(1,1)-N-3)(2)(L)(2)(DMSO)(2)] (2) [where HL = 3-(methyl-amino)propyliminomethyl-4-bromophenol, a tridentate Schiff base], have been synthesized and characterized by elemental analysis, IR, UV-Vis and fluorescence spectroscopy and single-crystal X-ray diffraction studies. The deprotonated tridentate Schiff base occupies three coordination sites of nickel(II) in each of the complexes. In the absence of any secondary coordinating anions, the octahedral geometry of nickel(II) in complex 1 is completed by the coordination of a second molecule of the tridentate Schiff base. On the other hand, in complex 2, the fourth coordination site of nickel(II) is occupied by an azide. A symmetry related azide from a different molecule coordinates the fifth site of nickel(II), thereby forming a double end-on azide bridged centrosymmertric dimer. An oxygen from a DMSO molecule occupies the sixth coordination site of nickel(II) to complete its octahedral geometry. There are hydrogen bonding and C-H center dot center dot center dot pi interactions within the dinuclear moiety of complex 2. A one-dimensional chain along the a axis is produced in complex 1 via a Br center dot center dot center dot Br interaction. (C) 2014 Elsevier Ltd. All rights reserved

Large magnetodielectric effect in nickel zinc ferrite–lithium niobate nanocomposite

Nanocomoposites of Ni_0.5Zn_0.5Fe₂O₄ (NZF) and LiNbO₃ were synthesized. The average diameter of nanoparticles was 9.5 nm and lithium niobate had a thickness of ∼2.5 nm. The sample showed room temperature (RT) ferromagnetism. A magneto-dielectric coefficient of 20% was observed at a magnetic field of 0.5 T. This was explained using inhomogeneous conductor model. It arose due to NZF resistance decrease by about 35% for the applied magnetic field. Nanoindentation studies on the sample showed a creep strain rate (∼10⁻³ s⁻¹) at RT. This was ascribed to a large grain boundary diffusion of Fe³⁺ ions in NZF phase

Magnetodielectric effect in Ni_0∙5Zn_0∙5Fe₂O₄–BaTiO₃ nanocomposites

Composites comprising of nanoparticles of Ni_0∙5Zn_0∙5Fe₂O₄ (NZF) and BaTiO₃ (BT), respectively were synthesized by a chemical method. The particles had diameters in the range of 15–31 nm. NZF was prepared by a coprecipitation technique. This was soaked in a sol containing BT. Compositions synthesized were xNZF-(1 – x) BT, where x = 0∙7, 0∙5 and 0∙3, respectively. The composites showed ferromagnetic hysteresis loops due to NZF phase. The analysis of coercivity variation as a function of temperature gave blocking temperatures in the range of 306–384 K depending on the diameter of the ferrite nanoparticles. This implied that superparamagnetic interactions are above these temperatures. The nanocomposites also exhibited ferroelectric behaviour arising due to the presence of BT. The remanent polarization of the samples was small. This was adduced to the nanosize of BT. The specimens showed magneto-dielectric (MD) effect in the magnetic field range 0–0∙7 Tesla. The MD parameter measured at the maximum magnetic field was around 2%. This was one order of magnitude higher than that reported so far in similar composite systems. This was explained on the basis of a two-phase inhomogeneous medium model with an interface between them, the phases possessing drastically different electrical conductivities

Dynamic Controller Deployment for Mixed-Grid Optical Networks

Co-existing fixed-grid and flex-grid (i.e., mixed-grid) optical networks introduce new challenges for network orchestration. Such mixed-grid networks are often controlled by hierarchical distributed architecture comprising of Optical Network Controllers and Software-Defined Network Controllers. Optimal deployment of these controllers is very important for efficient management of mixed-grid optical networks

A combined experimental and computational study of supramolecular assemblies in ternary copper(II) complexes with a tetradentate N-4 donor Schiff base and halides

Three new copper(II) complexes, [Cu(L)(Cl)]ClO4 (1), [Cu(L)(Br)]ClO4 (2) and [Cu(L)(I)]ClO4 (3), have been prepared from a tetradentate symmetrical Schiff base, N,N'-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L), and characterized by elemental analysis, IR and UV-Vis spectroscopy and single-crystal X-ray diffraction studies. Extended supra-molecular networks were generated through different weak noncovalent forces. Density functional theory (DFT) calculations were employed to estimate the contribution of each interaction in the formation of the assembly using several theoretical models. The interplay between the anion-pi and pi-pi interactions is also analyzed and a mutual reinforcement of both interactions is demonstrated. The assignment of the contribution of each interaction and its mutual influence is certainly important to shed light on the delicate mechanism that governs the molecular recognition and crystal packing

Synthesis, structure, magnetic property and self-assembly of two double end-on azide bridged ferromagnetic nickel(II) complexes with distinct bidentate blocking ligands: A combined experimental and theoretical study

Two centrosymmetric dinuclear nickel(II) complexes, [Ni-2(dmpn)(2)(hap)(2)(mu(1,1)-N-3)(2)] and [Ni-2(dmpn)(2)(hap)(2)(mu(1,1)-N-3)(2)], (dmpn=N,N-dimethyl-1,3-diaminopropane and Hhap = 2-hydroxyacetophenone, Hhan = 1-hydroxy-2-acetonaphthone) have been synthesized and characterized. Single crystal X-ray diffraction analyses confirm the structures of one of the tridentate Schiff bases used and both complexes. Variable temperature (1.8-300 K) magnetic susceptibility measurements indicate the presence of ferromagnetic coupling interactions among nickel(II) centers with J = 29(1) cm(-1) (in 1) and 15.62(2) cm(-1) (in 2). Calculated J values (37 cm(-1) in 1 and 31 cm(-1) in 2, respectively) are in agreement with the values obtained experimentally. C-H/pi interactions form supramolecular chains both in 1 and 2. DFT calculations reveal that C-H/pi interaction energies are large negative (Delta E-1 = -12.9 kcal/mol for 1 and Delta E-2 = -17.2 kcal/mol for 2) confirming the relevance of these interactions. The interactions have also been characterized by means of the non-covalent interaction (NCI) plot. (C) 2015 Elsevier Ltd. All rights reserved

Designed synthesis of CO2-promoted copper(II) coordination polymers: synthesis, structural and spectroscopic characterization, and studies of versatile functional properties

A series of CO2-promoted Cu(II) coordination polymers in different coordination environments has been synthesized. The molecular description and properties of the four complexes have been investigated by CHN, MS, UV-VIS, IR, PXRD, TEM, SQUID, SC-XRD, NLDFT, and electrical property characterizations. Single crystal X-ray structure determination of [Cu(bpy)(C2O4)]n (1) and [Cu(2-AMP)2(C2O4)]n (2) depicts their polynuclearity [bpy = 2,2’-bipyridine, 2-AMP = 2-aminopyridine; 2-AMP is a cleaved ligand of starting ligand L1 = N-(phenyl(pyridin-2-ylamino)methyl)pyridin-2-amine]. Both complexes have distorted octahedral geometry. Starting from another tripodal ligand L2 [L2 = 2-((((2-(pyridin-2-yl)ethyl)(pyridin-2-yl)-methyl)amino)methyl)phenol, L2’ (cleaved L2 ligand) = 2-(pyridin-2-yl)-N-((pyridin-2-yl)methyl)ethanamine], a mononuclear complex [Cu(L2)(Cl)] (3) has been obtained with a distorted square pyramidal geometry. Polynuclear complexes 1, 2, and 4 are CO2-mediated functional materials that have been produced in benzonitrile solvent medium. Interestingly, complex 4 of cleaved L2 ligand is a wonderful copper-based functional material with appreciable surface area. Powder XRD and TEM analysis of complex 4 supports its mesoporosity. Moreover, all four complexes can function as semiconductors over a wide temperature range