Search results for " anisotropy"
showing 10 items of 295 documents
Cyanide-bridged coordination polymers constructed from lanthanide ions and octacyanometallate building-blocks
2018
A new series of cyanide-bridged assemblies, {KH[Ln2(2,3-pzdc)2(CH3OH)(H2O)7][M(CN)8]}·5H2O (Ln3+ = Nd, Gd, Tb, and Dy; M4+ = Mo and W), were synthesised by self-assembling lanthanide ions and octacyanometallate ions in the presence of pyrazine-2,3-dicarboxylic acid (2,3-H2pzdc). These compounds have a 3D structure in which octagon-like Ln4M4(CN)8 rings are connected through a second Ln3+ center via the carboxylate groups of one 2,3-pzdc. The resulting 1D channels are filled with K+ ions and lattice water molecules. The temperature and field dependent magnetization studies as well as ab initio calculations indicate weak ferromagnetic interactions between the Gd3+ ions within the GdMo compoun…
Role of Orbital Degeneracy in the Single Molecule Magnet Behavior of a Mononuclear High-Spin Fe(II) Complex
2010
To explain the single-molecule magnet behavior of the mononuclear complex [(tpaMes)Fe](-) we have developed a model that takes into account the trigonal ligand field splitting of the atomic (5)D term of the Fe(II) ion, and the spin-orbital splitting and mixing of the ligand field terms. The ground ligand field term is shown to be the orbital doublet (5)E possessing an unquenched orbital angular momentum. We demonstrate that the splitting of this term cannot be described by the conventional zero-field splitting Hamiltonian proving thus the irrelevance of the spin-Hamiltonian formalism in the present case. The first-order orbital angular momentum is shown to lead to the strong magnetic anisot…
SIMPRE: A software package to calculate crystal field parameters, energy levels, and magnetic properties on mononuclear lanthanoid complexes based on…
2013
This work presents a fortran77 code based on an effective electrostatic model of point charges around a rare earth ion. The program calculates the full set of crystal field parameters, energy levels spectrum, and wave functions, as well as the magnetic properties such as the magnetization, the temperature dependence of the magnetic susceptibility, and the Schottky contribution to the specific heat. It is designed for real systems that need not bear ideal symmetry and it is able to determine the easy axis of magnetization. Its systematic application to different coordination environments allows magneto-structural studies. The package has already been successfully applied to several mononucle…
Multi-frequency EPR studies of a mononuclear holmium single-molecule magnet based on the polyoxometalate [Ho(III)(W5O18)2]9-.
2012
Continuous-wave, multi-frequency electron paramagnetic resonance (EPR) studies are reported for a series of single-crystal and powder samples containing different dilutions of a recently discovered mononuclear Ho(III) (4f(10)) single-molecule magnet (SMM) encapsulated in a highly symmetric polyoxometalate (POM) cage. The encapsulation offers the potential for applications in molecular spintronics devices, as it preserves the intrinsic properties of the nanomagnet outside of the crystal. A significant magnetic anisotropy arises due to a splitting of the Hund's coupled total angular momentum (J = L + S = 8) ground state in the POM ligand field. Thus, high-frequency (50.4 GHz) EPR studies reve…
Kinetics of doublet formation in bicomponent magnetic suspensions: The role of the magnetic permeability anisotropy
2017
Micron-sized particles (microbeads) dispersed in a suspension of magnetic nanoparticles, i.e., ferrofluids, can be assembled into different types of structures upon application of an externalmagnetic field. This paper is devoted to theoretical modeling of a relative motion of a pair of microbeads (either soft ferromagnetic or diamagnetic) in the ferrofluid under the action of applied uniform magnetic field which induces magnetic moments in the microbeads making them attracting to each other. The model is based on a point-dipole approximation for the magnetic interactions between microbeads mediated by the ferrofluid; however, the ferrofluid is considered to possess an anisotropic magnetic p…
1D antiferromagnetism in spin‐alternating bimetallic chains
1990
The magnetic and thermal properties of the ordered bimetallic chain CoNi(EDTA)⋅6H2O in the very low‐temperature range are reported. The magnetic behavior does not exhibit the characteristic features of 1D ferrimagnets, but a continuous decrease of χmT towards zero at absolute zero. This 1D antiferromagnetic behavior results from an accidental compensation between the moments located at the two sublattices. This behavior, as well as the specific‐heat results, are modeled on the basis of an Ising‐exchange model that considers both alternating spins and Landé factors, and a zero‐field splitting on the Ni site. Eugenio.Coronado@uv.es ; Fernando.Sapina@uv.es
Magnetic exchange interactions in the heteropoly complexes [M4(H2O)2(PW9O34)2]10− [M=Co(II) and Cu(II)]
1990
The magnetic properties of the heteropolyanions [M4(H2O)2(PW9O34)2]10− [M=Co(II) and Cu(II)] down to 4 K are reported. Their individual heteropoly molecules contain a rhomblike arrangement formed by four coplanar MO6 octahedra sharing edges. The magnetic properties support an intramolecular ferromagnetic exchange in the Co(II) tetramer, and antiferromagnetic exchange in the Cu(II) tetramer. These behaviors are discussed assuming anisotropic exchange in the Co(II) compound, and Heisenberg exchange in the Cu(II) compound. Carlos.Gomez@uv.es
Coupled stochastic dynamics of magnetic moment and anisotropy axis of a magnetic nanoparticle
2012
An algorithm is developed for numerical simulation of coupled stochastic dynamics of magnetic moment and magnetic anisotropy axis of a nanoparticle. Time-correlation functions of the magnetic moment and its components longitudinal and transverse to the magnetic anisotropy axis are calculated by averaging along the stochastic trajectory. The longitudinal and transverse relaxation times are found by fitting the time correlation functions. Existing theoretical relations derived by the effective field approach in the limit of small fields are confirmed. The time-correlation functions of magnetic moments of nanoparticles in dependence on their properties are calculated numerically for arbitrary …
Photoinduced magnetization wave in diluted magnetic semiconductors
2006
We derive an evolutional equation incorporating the processes of spin-polarization transfer from an electron to a magnetic ion subsystem of a diluted magnetic semiconductor along with spin-lattice relaxation and spatial spin diffusion. Above equation has been obtained for nonequilibrium magnetization due to exchange scattering of photoexcited charge carriers by magnetic ions. We show that the mechanism of a band gap narrowing due to exchange scattering requires relatively low optical power to reach an optical bistability for pump frequency range close to crystal band gap. In a bulk crystal, only relatively small local area with essential magnetization enhancement can absorb optical power, t…