Search results for "spin [structure function]"
showing 10 items of 1132 documents
The [Fe(etz)6](BF4)2 Spin-Crossover System—Part One: High-Spin ⇌ Low-Spin Transition in Two Lattice Sites
1996
The [Fe(etz),](BF,), spin-cross-over system (etz = 1-ethyl-1 H-tetrazole) crystallizes in space group P1, with the following lattice constants at 298 K: a 10.419(3), b=15.709(1), c = 18.890(2) A = = 71.223(9), =77.986(10), and = 84.62(1)° V = 2862.0(9) A3 and Z = 3. Two nonequivalent lattice sites, one without (site A) and one with (site B) inversion symmetry, are observed. The population of the two sites nA:nB is 2:l. Iron(II) on site A undergoes a thermal low-spin (LS) high-spin (HS) transition with T1/2I, = 105 K. whereas that on site B remains in the high-spin state down to cryogenic temperatures. Application of external pressure of up to 1200 bar between 200 and 60 K does not cause for…
A new 3-D polymeric spin transition compound: [tris(1,4-bis(tetrazol-1-yl)butane-N1,N 1′)iron(II)] bis(perchlorate)
2001
A series of novel polymeric compounds of formula [M(btzb)3][ClO4]2 (Mll = Fe, Ni or Cu) with btzb = 1,4-bis-(tetrazol-1-yl)butane have been prepared and their physical properties investigated. The btzb ligand has been prepared and its crystal structure determined, together with a tentative crystal structure of the 3-D compound [Fe(btzb)3][ClO4]2. The model of the latter shows two symmetry-related, interpenetrating Fe-btzb networks in which the iron(II) ions approach each other as close as 8.3 and 9.1 A. This supramolecular catenane undergoes a sharp thermal spin transition around 160 K with hysteresis (20 K) along with a pronounced thermochromic effect. The spin crossover behaviour has been…
Electronic and magnetic structure ofLa0.875Sr0.125MnO3calculated by means of hybrid density-functional theory
2007
We present the results of ab initio calculations on magnetic and electronic structures of La1�xSrxMnO3 at low doping, x =1/8. Using the B3LYP hybrid exchange-correlation functional within the framework of densityfunctional theory, we predict a ferromagnetic ground state for La0.875Sr0.125MnO3 in both the low-temperature orthorhombic and the high-temperature pseudocubic phases. This is in contrast to its parent compound LaMnO3, for which we find in agreement with experiment the layered antiferromagnetic state to be the most stable one. The calculated density of states and bond population analysis suggest a tendency of formation of half-metallic spin states in the band gap of both structures.
Mössbauer Emission Spectroscopy of Mixed-Valency after Nuclear Decay in Iron Complexes
1991
The population of anomalous spin states and aliovalent charge states of iron induced by the 57 Co(EC)57 Fe nuclear decay in polycristalline transition metal compounds was studied by means of Coincidence Mossbauer Emission Spectroscopy (CMES), that is Time-Differential Mossbauer Emission Spectroscopy (TDMES) as well as γ/Xray-Coincidence Mossbauer Emission Spectroscopy (γ/X-CMES). By use of time-integral Mossbauer emission spectroscopy (TIMES) we have observed anomalous high spin (S = 2) states of 57 Fe(II) in the system [57Co/Co(phen)3(ClO 4)2 with increasing intensities on lowering the temperature. With TDMES we followed quantitatively the high spin-low spin relaxation kinetics in this com…
ELECTRON SPIN RELAXATION PROCESS IN SILICON CRYSTALS
2014
Recently, electrical injection of spin polarization in n-type and p-type silicon has been experimentally carried out up to room-temperature. Despite of these preliminary but promising experimental results, a comprehensive theoretical framework concerning the influence of transport conditions on the phonon-induced spin depolarization process in silicon structures, in a wide range of values of temperature, doping concentration and amplitude of external fields, is still in a developing stage. In order to elucidate the electron transport and spin dynamics of conduction electrons in lightly doped n-type Si crystals we have performed semiclassical multiparticle Monte Carlo simulations and numeric…
Monte Carlo Simulation of Spin Relaxation of Conduction Electrons in Silicon
2014
Recently, electrical injection of spin polarization in n-type and p-type silicon up to room-temperature has been experimental- ly carried out. Despite of these promising experimental results, a comprehensive theoretical framework concerning the influence of transport conditions on the spin depolarization process in silicon structures, in a wide range of values of temperature, doping concentration and amplitude of external fields, is still in a developing stage. In this contribution we use a semiclassical multiparti- cle Monte Carlo approach to simulate the electron transport and spin dynamics in lightly doped n-type Si crystals and numerically calculate the spin lifetimes of drifting electr…
Liposomes modified by mono- and bis-phthalocyanines: A comprehensive EPR study.
2016
The impact of selected metallophthalocyanines, featuring diverse molecular structure, upon the fluidity of liposome membranes was studied using the spin label EPR technique. The “mono”-type MPc’s (M = Zn, Sn; Pc = C32H16N8 is the phthalocyanine ligand) and sandwich LnPc2 complexes (Ln = Nd, Sm, Gd) were explored. Liposomes were obtained in a sonication process, from egg yolk lecithin (EYL) in water. TEMPO and 16-DOXYL spin labels were used to monitor the peripheral and central part of the lipid double layer, respectively, which allowed to localize the phthalocyanine additive within the bilayer, as well as to perform independent measurements of changes in fluidity upon addition thereof. All …
Communication between iron(II) building blocks in cooperative spin transition phenomena
2003
[EN] In the present article we discuss the cooperative nature of the spin crossover phenomenon in iron(II) complexes, providing a perspective of the state of the art in this area. The first aspect we discuss is the role of the intermolecular interactions, more precisely the ¿-interactions, in mononuclear complexes. We show that by playing with the nature of the ligands, aliphatic, aromatic, or extended aromatic, it is possible to create stronger cohesive forces and receive a more cooperative response from the compound. In the next step the singular family of bipyrimidine-bridged iron(II) dinuclear compounds is presented as the simplest example of polynuclear spin crossover complexes exhibit…
Shape coexistence in neutron-deficient Hg isotopes studied via lifetime measurements in Hg-184,Hg-186 and two-state mixing calculations
2014
Abstract: The neutron-deficient mercury isotopes, 184 , 186 Hg, were studied with the recoil distance Doppler-shift method using the Gammasphere array and the K ̈ oln plunger device. The differential decay curve method was employed to determine the lifetimes of the yrast states in 184 , 186 Hg. An improvement on previously measured values of yrast states up to 8 + is presented as well as first values for the 9 3 state in 184 Hg and 10 + state in 186 Hg. B ( E 2) values are calculated and compared to a two-state mixing model which utilizes the variable moment of inertia model, allowing for extraction of spin-dependent mixing strengths and amplitudes. peerReviewed
Structural and Electrochemical Analysis of CIGS: Cr Crystalline Nanopowders and Thin Films Deposited onto ITO Substrates
2021
A new approach for the synthesis of nanopowders and thin films of CuInGaSe2 (CIGS) chalcopyrite material doped with different amounts of Cr is presented. The chalcopyrite material CuInxGa1 − xSe2 was doped using Cr to form a new doped chalcopyrite with the structure CuInxCryGa1 − x − ySe2, where x = 0.4 and y = 0.0, 0.1, 0.2, or 0.3. The electrical properties of CuInx CryGa1 − x − ySe2 are highly dependent on the Cr content and results show these materials as promising dopants for the fabrication thin film solar cells. The CIGS nano-precursor powder was initially synthesized via an autoclave method, and then converted into thin films over transparent substrates. Both crystalline precursor p…