Search results for "Néel temperature"
showing 10 items of 21 documents
Evidences for the Formation of Chromium in the Unusual Oxidation State Cr(IV)
1999
Abstract Magnetic measurements on Tl x Cr 5 Se 8 (0≤ x ≤1) reveal that stoichiometric TlCr 5 Se 8 is a three-dimensional antiferromagnet with a Neel temperature T N of about 55 K. In contrast, samples with a reduced Tl content show highly unusual magnetic properties that are without precedent in the literature of magnetically coupled systems: upon lowering the temperature from 300 K the susceptibility reaches a maximum at about 125 K and then steeply drops to a value comparable to that obtained at room temperature. The height of this maximum increases first with decreasing Tl abundance reaching its largest value at a composition Tl 0.2 Cr 5 Se 8 and then decreases again for samples with x 3…
Néel Transition of Lattice Fermions in a Harmonic Trap: A Real-Space Dynamic Mean-Field Study
2010
We study the magnetic ordering transition for a system of harmonically trapped ultracold fermions with repulsive interactions in a cubic optical lattice, within a real-space extension of dynamical mean-field theory. Using a quantum Monte Carlo impurity solver, we establish that antiferromagnetic correlations are signaled, at strong coupling, by an enhanced double occupancy. This signature is directly accessible experimentally and should be observable well above the critical temperature for long-range order. Dimensional aspects appear less relevant than naively expected.
One-dimensional iron(III) and two-dimensional iron(III)nickel(II) cyanide-bridged ferromagnetic arrays from hexacyanoferrate(III) and [Ni(cyclam)]2+ …
1999
Abstract The X-ray structures and magnetic properties of a iron(III) linear chain and a honeycomb-like layered iron(III)-nickel(II) cyanide-bridged compound are reported. The former contains alternating iron sites and unexpected ferromagnetic behaviour, justified on the basis of the axial distortion from regular octahedral geometry of one of the iron ions. The latter is metamagnetic with ferromagnetic intralayers and antiferromagnetic interlayers interactions with a Neel temperature, TN= 7.7 K. The field-induced transition from an antiferro- to a ferromagnetic state takes place at Hc= 5000 G. The antiferromagnetic ordered phase exhibits spin-canting and long range ferromagnetic ordering at …
Pressure induced increase in Tc for the organic-based magnet FeII(TCNE)2 (TCNE=tetracyanoethylene)
2013
Abstract Pressure dependent magnetization and 57Fe Mossbauer studies were performed on Fe(TCNE)[C4(CN)8]1/2·zCH2Cl2 (TCNE = tetracyanoethylene). Pressure did not influence the Mossbauer parameters in paramagnetic state. Mossbauer data reveals the onset of magnetic ordering at 130 K and significant enhancement of the magnetic ordering temperature from 100 to 150 K accompanied by an increase of the spontaneous magnetization, which is higher than reported from the magnetic data, and application of pressure induces the reversible formation of a new, metastable magnetic species. These changes suggest an increase of the dimensionality of magnetic interaction, i.e., stronger interlayer coupling. A…
X-ray investigation and discussion of the magnetostriction of Gd3T(T= Ni, Rh, Irx) single crystals
2000
The variations of the lattice parameters of Gd3T(T= Ni, Rh, Irx) single crystals with temperature were measured in the range 10–300 K. The compounds with Ni and Rh crystallize in the orthorhombic space groupPnma, but the compound with Ir crystallizes as Gd5Ir2in the monoclinic space groupA2/a. The three compounds exhibit an anomalous anisotropic spontaneous magnetostriction below the magnetic ordering temperature.
Tuning up the Tc in Mn(II)Cu(II) bimetallic planes and design of molecular-based magnets
1998
Abstract A family of related compounds of general formula (PPh4)2Mn2[Cu((L)]3nH2O, where PPh4+ is the tetraphenylphosphonium cation and L stands for ortho-phenylenebis(oxamate) (opba, 1), ortho-phenylene (N′-methyloxamidate) (oxamate) (Meopba, 2) and ortho-phenylenebis (N′-methyloxamidate) (Me2opba, 3), have been synthesized. The X-ray absorption near-edge structure (XANES) and extended X-ray Within absorption fine structure (EXAFS) spectra at both Mn and Cu K-edges for all three compounds, as well as their powder X-ray patterns, are consistent with a layered structure built up of parallel Mn11Cu11 two-dimensional honeycomb networks separated by PPh4+ cations. Within the antonic metallic la…
Synthesis and characterization of a new layered organic-inorganic hybrid nickel(II) 1,4 : 5,8-naphthalenediimide bis-phosphonate, exhibiting canted a…
2008
A new Ni(II) layered hybrid organic-inorganic compound of formula Ni{sub 2}[(NDI-BP)(H{sub 2}O){sub 2}].2H{sub 2}O has been prepared in very mild conditions from N,N'-bis(2-phosphonoethyl)napthalene-1,4:5,8-tetracarboximide (NDI-BP ligand) and NiCl{sub 2}. The X-ray powder structure characterization of the title compound suggests a pillared layered organic-inorganic hybrid structure. The distance between the organic and inorganic layers has been found to be 17.8 A. The inorganic layers consist of corner sharing [NiO{sub 5}(H{sub 2}O)] octahedra and they are pillared by the diphosphonate groups. DC and AC magnetic measurements as a function of temperature and field indicate the presence of 2…
Magnetic Properties of DyTe
1997
The magnetic properties of the lanthanide chalcogenides are much less explored than the monopnictides. The main reasons are probably difficulties in syntheses and the crystals growth. In particular, the properties of monotellurides are almost completely unknown. The dysprosium tellurides: DyTe and Dy2Τe3, crystallize in the structures related to the rock salt type. The first compound is metallic, while the second — semiconducting. Dysprosium sesquitelluride behaves like a simple antiferromagnet with the Neel temperature equal to 4.1 K [1]. We synthesized and investigated the dysprosium monnotelluride in order to examine a change of exchange interactions after transition to the metallic stat…
Uncompensated magnetization in the layered molecular antiferromagnet {N(n-C5H11)4[MnIIFeIII(ox)3]}∞
2009
Abstract Studies on the magnetic properties of the molecular antiferromagnetic material {N( n -C 5 H 11 ) 4 [Mn II Fe III (ox) 3 ]} ∞ , carried out by various physical techniques (AC/DC magnetic susceptibility, magnetization, heat capacity measurements and Mossbauer spectroscopy) at low temperatures, have been presented. Different experimental observations complement each other and provide a clue for the observation of an uncompensated magnetization below the Neel temperature and short-range correlations persisting high above T N . It is understood that the honeycomb layered structure of the compound contains non-equivalent magnetic sub-lattices, (Mn II –ox–Fe III A –...) and (Mn II –ox–Fe …
Magnetic properties of quasi-2D antiferromagnet {N(n-C5H11)4[MnIIFeIII(ox)3]}∞ below Néel temperature: revisited
2004
Abstract Magnetic measurements of {N(n-C 5 H 11 ) 4 [Mn II Fe III (ox) 3 ]} ∞ were carried out in the 5–300 K temperature range under different applied magnetic fields up to 50 kOe with zero-field-cooled (ZFC) and field-cooled (FC) modes. The FC and ZFC χ ( T ) plots exhibited a significantly large bifurcation below the transition temperature, which was traceable even at 50 kOe of applied magnetic field. The bifurcation temperature was found to be magnetic field dependent for the lower range of magnetic fields, which can be represented by a polynomial of magnetic field. The observed magnetic transition temperature of this compound was in good agreement with the earlier reported results. The…