Search results for "Curie"
showing 10 items of 110 documents
Design and Experimental Test of a Thermomagnetic Motor
2012
Abstract This paper presents a Thermomagnetic Motor. The design of the motor is based on a thermal-magnetic coupled dynamic model, which is obtained by assuming the use of a ferromagnetic material working at temperatures near the curie point. The motor is modeled in terms of both its magnetic as well thermal properties (magnetic permeability and thermal conductivity) and the thermal processes are supposed to be influenced by the thermal conductivity, the convection and the advection. An analytical expression of the generated torque, which links this quantity to the magnetic, thermal and geometrical parameters of the generated torque is given. A design of a machine, based on this theory is p…
Synthesis, crystal structure and magnetic properties of [Cu(bpym)(mal)(H2O)]·6H2O and [Cu2(bpym)(mal)2(H2O)2]·4H2O (bpym=2,2′-bipyrimidine, H2mal=mal…
2001
Abstract Two new mixed-ligand complexes of formula [Cu(bpym)(mal)(H2O)]·6H2O (1) and [Cu2(bpym)(mal)2(H2O)2]·4H2O (2) (bpym=2,2′-bipyrimidine and H2mal=malonic acid) have been synthesised and characterised by X-ray diffraction methods. The crystal structure of 1 consists of mononuclear [Cu(bpym)(mal)(H2O)] units in which the copper atom shows a slightly distorted square-pyramidal environment with two bpym-nitrogen and two malonate-oxygen atoms forming the equatorial plane and a water molecule in the axial position. The structure of 2 is built by centrosymmetric bpym-bridged dinuclear [Cu2(bpym)(mal)2(H2O)2] units, in which the geometry of each Cu(II) ion is similar to that found in 1. Malon…
Crystal Field Excitations in CeAgl−xInx Compounds
1982
The substitution of the monovalent Ag for the trivalent In in LaAgl−xInx and CeAgl−xInx offers the possibility of influencing the conduction electron system in these compounds. The strong dependence of the spin susceptibility of La-systems on the In-concentration1 was interpreted by band calculations which suggest that the Fermi level is pushed into a region of a high 5d-eg-band density of states2. Furthermore, CeAgl−xInx is one of the rare 4f systems where a structural phase transition (from cubic to tetragonal) occurs prior to magnetic ordering. The ferromagnetic Curie temperature TC is roughly independent of x whereas the structural transition temperature Ts rises from 15 K for CeAg to a…
Synthesis, Chirality, and Magnetic Properties of Bimetallic Cyanide-Bridged Two-Dimensional Ferromagnets
2006
The assembly of hexacyanoferrate(III) anions and nickel(II) bis-diamino complexes of the chiral ligand trans-cyclohexane-1,2-diamine (trans-chxn) yields cyanide-bridged two-dimensional ferromagnets of the general formula [Ni(trans-chxn)2]3[Fe(CN)6]2‚2H2O. Their crystal structure is built from cyanide-bridged bimetallic planes separated by the bulky chxn ligands, giving rise to a large interlayer distance ( d ) 11.7 A). These materials order ferromagnetically at the Curie temperature TC ) 14 K. AC susceptibility measurements evidence an unusual magnetic behavior below TC, with a marked frequency dependence. A thorough magnetic analysis demonstrates that this complex behavior is due to the pi…
Magnetic Transitions in the Double Perovskite Sr2FeRe1-xFexO6(0≤X≤0.5)
2008
AbstractThe synthesis, structure, and magnetic and transport properties of solid solutions Sr2FeRe1-xFexO6 (0≤x≤0.5) are reported. A structural evolution in the solid solutions from a double perovskite to perovskite is observed with increasing Fe/Re disorder. Except for the metallic parent compound all members of the series are semiconducting. For the Fe-doped samples a change from ferrimagnetic interactions in the parent compound to a complex superposition of ferrimagnetic and antiferromagnetic interactions was observed. The magnetic moment decreases with x, whereas the Curie temperature TC remains unaffected. The magnetic and Mössbauer data suggest Fe to act as a redox-buffer.
Crystal structure and magnetism of the double perovskites A2FeReO6 (A=Ca, Sr, Ba)
2004
Abstract We synthesized a series of double perovskites A 2 FeReO 6 (A=Ca, Sr, Ba) with Curie temperatures above room-temperature. Neutron and X-ray diffraction analysis have been performed in order to determine the structural and (local) magnetic properties of these materials. While Ba 2 FeReO 6 stays cubic over the whole temperature range we examined, the Sr-compound shows a tetragonal distortion of the perovskite structure which does not completely vanish up to about 520 K far above T C . Ca 2 FeReO 6 has a monoclinic unit cell at high temperatures. Below 400 K a phase separation in two monoclinic phases with identical cell volume is observed in neutron scattering.
Magnetization and61Ni Mössbauer effect study of the ternary arsenide CrNiAs
2008
The results of x-ray diffraction, dc magnetization, and 61Ni M?ssbauer spectroscopy studies of the ternary arsenide CrNiAs are reported. This compound crystallizes in the orthorhombic Fe2P-type structure (space group ) with the lattice parameters a = 6.1128(2)?? and c = 3.6585(1)??. CrNiAs is a mean-field ferromagnet with Curie temperature TC = 171.9(1)?K and the critical exponents ? = 0.514(18), ? = 1.010(16), and ? = 2.922(10). The temperature dependence of the magnetic susceptibility above TC follows the modified Curie?Weiss law with a paramagnetic Curie temperature of 176.0(3)?K and effective magnetic moment per transition metal atom of 2.42(1)??B. The magnetic moment per formula unit a…
Grain-size-induced relaxor properties in nanocrystalline perovskite films
2004
Thin films of ${\mathrm{Pb}}_{0.76}{\mathrm{Ca}}_{0.24}{\mathrm{TiO}}_{3}$ (PTC), which is a classical ferroelectric as a bulk material and of the relaxor material $\mathrm{Pb}({\mathrm{Sc}}_{0.5}{\mathrm{Nb}}_{0.5}){\mathrm{O}}_{3}$, have been produced to find out whether nanocrystalline ferroelectric films show a grain-size-induced relaxor behavior. Amorphous films were deposited onto a $\mathrm{Ti}∕\mathrm{Pt}$ coated silicon (100) wafer by reactive $\text{rf}$ sputtering. Different grain sizes were prepared by a controlled annealing process and they were determined by profile analysis of x-ray diffraction spectra. Temperature dependent Raman spectroscopy was used to look for phase trans…
Itinerant Electron Metamagnetism in η-Carbide-Type Compound Co3Mo3C
2010
We report the magnetic properties of the cobalt molybdenum η-carbide-type compounds Co 3 Mo 3 C and Co 3 Mo 3 N. The magnetic susceptibility χ of Co 3 Mo 3 C shows a Curie–Weiss temperature dependence at high temperatures and a broad maximum at around 100 K, whereas that of Co 3 Mo 3 N shows a nearly temperature-independent enhanced Pauli paramagnetic behavior. The absence of a magnetic long-range order was confirmed by the nuclear magnetic resonance technique in both the compounds. As expected from the broad maximum of χ, we observed an itinerant electron metamagnetic transition at around 37 T in Co 3 Mo 3 C.
Geometric, electronic, and magnetic structure ofCo2FeSi: Curie temperature and magnetic moment measurements and calculations
2005
In this work a simple concept was used for a systematic search for materials with high spin polarization. It is based on two semiempirical models. First, the Slater-Pauling rule was used for estimation of the magnetic moment. This model is well supported by electronic structure calculations. The second model was found particularly for ${\mathrm{Co}}_{2}$ based Heusler compounds when comparing their magnetic properties. It turned out that these compounds exhibit seemingly a linear dependence of the Curie temperature as function of the magnetic moment. Stimulated by these models, ${\mathrm{Co}}_{2}\mathrm{FeSi}$ was revisited. The compound was investigated in detail concerning its geometrical…