Search results for "Curie"
showing 10 items of 110 documents
New CpCrCl2(PR3) complexes: physical properties and reduction chemistry
1998
Abstract Compounds CpCrCl2L ( L = PMe 2 Ph , 1 , PMePh 2 , 2 ; PPh 3 , 3 ) have been prepared. Their magnetic moment is in accord with the presence of three unpaired electron and a variable temperature 1H NMR investigation of 1 shows Curie-Weiss behavior. The 1H NMR, EPR and UV-visible spectra are in agreement with those of other previously reported compounds of the same family. An electrochemical investigation shows the accessibility of an irreversible reduction process. A parallel sodium reduction investigation of complexes CpCrCl2L (L = PMe3 and η1-dppe) suggests tjat the reduction process is followed by immediate chloride loss, and then by a ligand redistribution process to afford chrom…
Synthesis Crystal Structure and Magnetic Properties of the Trinuclear Nickel(II) Complex Bis[(μ-thiocyanato-N)bis(μ-pyridazine-N1,N2)bis(thiocyanato-…
2000
Unusual single N-bridging thiocyanato and double pyridazine (pdz) bridges occur in the linear trinuclear nickel(II) complex of formula [Ni3(pdz)6(NCS)6]. The compound exhibits a quasi Curie law behavior, the antiferromagnetic coupling through the double 1,2-diazine links being nearly compensated by the ferromagnetic exchange through the single N-bridging thiocyanato.
Transport and magnetic properties of La1−xCaxMnO3-films (0.1<x<0.9)
2000
Abstract By laser ablation we prepared thin films of the colossal magnetoresistive compound La1−xCaxMnO3 with doping levels 0.1 10 13 Ω have been measured with an electrometer setup. While the transport data indicate polaronic transport for the metallic samples above the Curie temperature the low-doped ferromagnetic insulating samples show a variable range hopping like transport at low-temperature.
Magnetic ordering in an (Fe0.2Cr0.8)1.5[Cr(CN)6] Prussian blue analogue studied with synchrotron radiation based spectroscopies
2018
The appearance of magnetic order in the (Fe0.2Cr0.8)1.5[Cr(CN)6]·15H2O Prussian blue analogue at low temperature has been investigated by means of synchrotron radiation-based X-ray absorption spectroscopy and X-ray magnetic circular dichroism. With the help of ligand field multiplet analysis we have been able to identify the oxidation states of the metallic cations present in the sample and their evolution with temperature. Our experiments reveal that the appearance of ferromagnetic order is triggered by the transformation of CrIII cations to CrII high-spin caused by a transfer of electrons from the Fe to the Cr resulting in an increase of the magnetic interactions within the (Cr, Cr) subla…
All-cis-1,2,3,4,5,6-cyclohexanehexacarboxylate two-dimensional gadolinium(III) complexes: Synthesis, X-ray crystal structure and magnetic properties
2010
Abstract The first gadolinium(III) complexes with the trideprotonated form of the 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (H3clhex3−) of formulae [Gd(H3clhex)(H2O)4]n·3nH2O (1) and [Gd(H3clhex)(H2O)4]n·6nH2O (2) have been prepared through the gel technique and their structures determined by single crystal X-ray diffraction. The structure of 1 is made up of 63 honey-comb layers which are generated by [Gd(H2O)4]3+ cations and H3clhex3− anions acting as three-fold nodes and three-fold connectors, respectively. The structure of 2 consists of a [44,62] two-dimensional network extended in the ac plane where the H3clhex−3 groups act as four-fold connectors and the [Gd(H2O)4]3+ units as four-fol…
Magnetic and structural properties of the double-perovskite Ca2FeReO6
2002
Abstract We suceeded in the preparation of polycrystalline Ca2FeReO6 which has a Curie temperature TC of 540 K, the highest value of all magnetic perovskites investigated till now. This material has been characterised by X-ray and neutron powder diffraction. We found at 548 K, a monoclinic unit cell (space group P21/n) with a=5.4366(5) A , b=5.5393(5) A , c=7.7344(5) A , and β=90.044(4)°. For temperatures below 400 K, a phase separation in two monoclinic phases with identical cell volume is observed in neutron scattering. The two phases possess different magnetic structure and coercivity. The conductivity is thermally activated for all temperatures and no significant magnetoresistivity is o…
Nonequilibrium magnetization dynamics of gadolinium studied by magnetic linear dichroism in time-resolved 4f core-level photoemission.
2008
The magnetic linear dichroism of the gadolinium 4f core level is studied in a time-resolved photoemission experiment employing laser pump- and synchrotron-radiation probe pulses. Upon optical excitation of the 5d6s valence electrons with femtosecond laser pulses, the magnetic order in the 4f spin system is reduced. Remarkably, the linear dichroism remains at 80% of the equilibrium contrast while the lattice temperature reaches the Curie temperature due to electron-phonon scattering. Contrasting itinerant ferromagnets, this shows that equilibration between the lattice and spin subsystems takes in Gd about 80 ps and is established in parallel with heat diffusion.
Magnetic properties and61Ni Mössbauer spectroscopy of the ternary phosphide CrNiP
2008
The results of x-ray diffraction, dc magnetization, and 61Ni Mossbauer spectroscopy studies of the ternary phosphide CrNiP are reported. This compound crystallizes in the orthorhombic Co2P-type structure (space group Pnma) with the lattice parameters a = 5.7965(1) A, b = 3.5337(1) A, and c = 6.8123(2) A. NiCrP is a ferromagnet with Curie temperature TC = 135.1(1) K. The ferromagnetic-to-paramagnetic transition is characterized by the critical exponents β = 0.355(22), γ = 1.241(18), and δ = 4.585(20). Their values are close to those of a 3D Heisenberg ferromagnet. The temperature dependence of the magnetic susceptibility above TC follows the modified Curie–Weiss law with a paramagnetic Curie…
Quaternary Heusler compounds Co(2-x)Rh(x)MnZ (Z = Ga, Sn, Sb): crystal structure, electronic structure, and magnetic properties.
2012
Within the huge family of Heusler compounds only a few quaternary derivatives are known that crystallize in the F43m space group. In this work, the yet unreported compounds CoRhMnZ (Z = Ga, Sn, Sb) and the alloy Co(0.5)Rh(1.5)MnSb were investigated in detail by experimental techniques and theoretical methods. The ab initio calculations predict the CoRhMnZ compounds to be half-metallic ferromagnets or to be close to the half-metallic ferromagnetic state. Calculations of the elastic constants show that the cubic structure is stable in compounds containing Mn. Both calculations and experiment reveal that Mn cannot be exchanged by Fe (CoRhFeGa). The low temperature magnetization of the compound…
High-temperature transport properties of La0.67Ca0.33MnO3 films
1999
Abstract The giant negative magnetoresistance in manganites has been investigated from the Curie temperature T c up to 600 K (2.6 T c ) in magnetic fields up to 8 T. Nonadiabatic small polaron hopping can successfully describe the temperature dependence of the resistivity. The magnetic field influence on the activation energy is explained by the interaction of unclustered ions with small spin clusters of four ions.