Search results for "Ferro"
showing 10 items of 2451 documents
The manifestation of dipoles clustering in paraelectric phase of disordered ferroelectrics
2001
Abstract We predict the existence of Griffiths phase in the dielectrics with concentrational crossover between dipole glass (electric analog of spin glass) and ferroelectricity. The peculiar representatives of above substances are KTaO3: Li, Nb, Na or relaxor ferroelectrics like Pb1−xLaxZr0.65Ti0.35O3. Since this phase exists above ferroelectric phase transition temperature (but below that temperature for ordered substance), we call it “para-glass phase”. We assert that the difference between paraelectric and para-glass phase of above substances is the existence of clusters (inherent to “ordinary” Griffiths phase in Ising magnets) of correlated dipoles. We show that randomness play a decisi…
Self-assembly, metal binding ability, and magnetic properties of dinickel(II) and dicobalt(II) triple mesocates
2012
Two metallacyclic complexes of general formula Na-8[(M2L3)-L-II]center dot xH(2)O [M = Ni (4) and Co (5) with x = 15 (4) and 17 (5)] have been self-assembled in aqueous solution from N,N'-1,3-phenylenebis(oxamic acid) (H4L) and M2+ ions in a ligand/metal molar ratio of 3 : 2 in the presence of NaOH acting as base. X-Ray structural analyses of 4 and 5 show triple-stranded, dinuclear anions of the meso-helicate-type (so-called mesocates) with C-3h molecular symmetry. The two octahedral metal-tris(oxamate) moieties of opposite chiralities (Delta, Lambda form) are connected by three m-phenylene spacers at intermetallic distances of 6.822(2) (4) and 6.868(2) angstrom (5) to give a metallacryptan…
Element-specific ferromagnetic resonance in epitaxial Heusler spin valve systems
2011
Time-resolved x-ray magnetic circular dichroism was used to investigate epitaxial MgO(100)/Co2Cr0.6Fe0.4Al and MgO(100)/Co2Cr0.6Fe0.4Al/Cr/CoFe films. The precessional motion of the individual sublattice magnetization, excited by continuous microwave excitation in the range 2–10 GHz, was detected by tuning the x-ray photon energy to the L 3 absorption edges of Cr, Fe and Co. The relative phase angle of the sublattice magnetization's response is smaller than the detection limit of 2°. A weakly antiferromagnetically coupled CoFe layer causes an increase in the ferromagnetic resonance linewidth consisting of a constant offset and a component linearly increasing with frequency that we partly at…
Room temperature antiferromagnetic resonance and inverse spin-Hall voltage in canted antiferromagnets
2021
We study theoretically and experimentally the spin pumping signals induced by the resonance of canted antiferromagnets with Dzyaloshinskii-Moriya interaction and demonstrate that they can generate easily observable inverse spin-Hall voltages. Using a bilayer of hematite/heavy metal as a model system, we measure at room temperature the antiferromagnetic resonance and an associated inverse spin-Hall voltage, as large as in collinear antiferromagnets. As expected for coherent spin pumping, we observe that the sign of the inverse spin-Hall voltage provides direct information about the mode handedness as deduced by comparing hematite, chromium oxide and the ferrimagnet yttrium-iron garnet. Our r…
Single-Molecule-Magnet Fe Fe and Antiferromagnetic Fe Coordination Clusters
2019
Supported by endogenous (part of the ligand, in-built) phenoxo bridges provided by the ligand 2,6-bis[{{(5-bromo-2-hydroxybenzyl)}{(2-(pyridylethyl)}amino}methyl]-4-methylphenol) (H3L), in its deprotonated form, exogenous (not part of the ligand, externally added or generated) oxo-/hydroxo- and acetato-bridged [FeII4FeIII2(O)2(O2CMe)4(L)2]·4Et2O (1) and [FeIII4(OH)2(O2CMe)3(L)2](ClO4)·3MeCN·2H2O (2) coordination clusters have been synthesized and structurally characterized. Complexes 1 and 2 have μ4-O and μ3-OH bridges, respectively. Magnetic studies on 1 reveal slow magnetic relaxation below 2 K. Both in-phase ( χ'M) and out-of-phase (χ″M) magnetic susceptibility were found to be frequency…
Magnetic behavior control in niccolite structural metal formate frameworks [NH2(CH3)2][Fe(III)M(II)(HCOO)6] (M = Fe, Mn, and Co) by varying the dival…
2010
By changing template cation but introducing trivalent iron ions in the known niccolite structural metal formate frameworks, three complexes formulated [NH(2)(CH(3))(2)][Fe(III)M(II)(HCOO)(6)] (M = Fe for 1, Mn for 2, and Co for 3) were synthesized and magnetically characterized. The variation in the compositions of the complexes leads to three different complexes: mixed-valent complex 1, heterometallic but with the same spin state complex 2, and heterometallic heterospin complex 3. The magnetic behaviors are closely related to the divalent metal ions used. Complex 1 exhibits negative magnetization assigned as Neel N-Type ferrimagnet, with an asymmetric magnetization reversal in the hysteres…
A family of enneanuclear iron(II) single-molecule magnets.
2008
Complexes [Fe 9 (X) 2 -(02CMe)8{(2-py) 2 CO 2 } 4 ] (X - = OH (1), N 3 - (2), and NCO- (3)) have been prepared by a route previously employed for the synthesis of analogous Co 9 and Ni 9 complexes, involving hydroxide substitution by pseudohalides (N 3 - , NCO-). As indicated by DC magnetic susceptibility measurements, this substitution induced higher ferromagnetic couplings in complexes 2 and 3, leading to higher ground spin states compared to that of 1. Variable-field experiments have shown that the ground state is not well isolated from excited states, as a result of which it cannot be unambiguously determined. AC susceptometry has revealed out-of-phase signals, which suggests that these…
Atomic, electronic and thermodynamic properties of cubic and orthorhombic LaMnO3 surfaces
2009
We studied in detail the atomic and electronic structure of the LaMnO3 surfaces, in both cubic and orthorhombic phases, combining GGA-plane wave approach, as implemented into the VASP-4.6.19 computer code, with a slab model. These studies are complemented by a thermodynamic analysis of the surface stability at different gas pressures and temperatures. The obtained results are compared with similar studies for other ABO3-perovskites. 2008 Elsevier B.V. All rights reserved. The ABO3-type perovskite manganites and cobaltates (A = La, Sr, Ca; B = Mn, Co) are important functional materials with numerous high-tech applications [1]. Some of them require understanding and control surface properties…
Electronic Structure Modulation in an Exceptionally Stable Non-Heme Nitrosyl Iron(II) Spin-Crossover Complex
2016
The highly stable nitrosyl iron(II) mononuclear complex [Fe(bztpen)(NO)](PF6)(2) (bztpen=N-benzyl-N,N',N'-tris(2-pyridylmethyl)ethylenediamine) displays an S=1/2 S=3/2 spin crossover (SCO) behavior (T-1/2=370 K, Delta H= 12.48 kJmol(-1), Delta S=33 JK(-1) mol(-1)) stemming from strong magnetic coupling between the NO radical (S=1/2) and thermally interconverted (S=0 S=2) ferrous spin states. The crystal structure of this robust complex has been investigated in the temperature range 120-420 K affording a detailed picture of how the electronic distribution of the t(2g)-e(g) orbitals modulates the structure of the {FeNO}(7) bond, providing valuable magneto-structural and spectroscopic correlat…
Modulation of Nuclearity in Cu II −Mn II Complexes of a N 2 O 2 Donor Ligand Depending upon Carboxylate Anions: Structures, Magnetic Properties and C…
2020
Three new hetero-metallic copper(II)-manganese(II) complexes, [(CuL)2 Mn3 (C6 H5 CO2 )6 ] (1), [(CuL)2 Mn(CH3 CO2 )2 ] (2), and {[(CuL)2 Mn(C6 H5 CH2 CO2 )2 ] ⋅ 2CH3 CN} (3), have been synthesized using [CuL] as ''metalloligand'' (where H2 L=N,N'-bis(2-hydroxynaphthyl-methylidene)-1,3-propanediamine). Single-crystal structural analyses show an almost linear penta-nuclear structure for complex 1 where a square planar [CuL] unit is connected to each of the two terminal MnII ions of a linear, centrosymmetric [Mn3 (benzoate)6 ] unit through the double phenoxido bridges. Both complexes 2 and 3 possess a linear tri-nuclear structure where two terminal square-pyramidal [CuL] units are bonded to th…