Search results for "SPIN STATES"
showing 10 items of 253 documents
Spin state of a single-molecule magnet (SMM) creating long-range ordering on ferromagnetic layers of a magnetic tunnel junction – a Monte Carlo study
2021
Paramagnetic single-molecule magnets (SMMs) interacting with the ferromagnetic electrodes of a magnetic tunnel junction (MTJ) produce a new system. The properties and future scope of new systems differ dramatically from the properties of isolated molecules and ferromagnets. However, it is unknown how far deep in the ferromagnetic electrode the impact of the paramagnetic molecule and ferromagnet interactions can travel for various levels of molecular spin states. Our prior experimental studies showed two types of paramagnetic SMMs, the hexanuclear Mn6 and octanuclear Fe–Ni molecular complexes, covalently bonded to ferromagnets produced unprecedented strong antiferromagnetic coupling between …
The Use of Polyoxometalates in the Design of Layer‐Like Hybrid Salts Containing Cationic Mn 4 Single‐Molecule Magnets
2013
Herein, we describe the combination of polyoxometalates (POMs) with a polynuclear metallic cluster Mn4 {Mn4 = [Mn4(OAc)2(pdmH)6]2+, (pdmH = deprotonated pyridine-2,6-dimethanol; C7H8NO2)} for the construction of ionic crystals with layered architectures. Choosing a POM with the appropriate charge and size not only allows for the fine tuning of the stacking periodicity, but it also allows modifying the in-plane packing motif and density of the cationic metallic clusters. The isolation of differently layered hybrid crystals with the same Mn4 single-molecule-magnet (SMM) system allowed for the direct comparison of the magnetic properties of such materials. The variation of the slow relaxation …
On the Nature of the Plateau in Two-Step Dinuclear Spin-Crossover Complexes
2004
A remarkable feature of the spin-crossover process in several dinuclear iron(II) compounds is a plateau in the two-step transition curve. Up to now, it has not been possible to analyse the spin state of dinuclear pairs that constitute such a plateau, due to the relative high temperatures at which the transition takes place in complexes investigated so far. We solved this problem by experimentally studying a novel dinuclear spin-crossover compound [[Fe(phdia)(NCS)(2)](2)(phdia)] (phdia: 4,7-phenanthroline-5,6-diamine). We report here on the synthesis and characterisation of this system, which exhibits a two-step spin transition at T(c1)=108 K and T(c2)=80 K, displaying 2 K and 7 K wide therm…
Bidirectional photo-switching of the spin state of iron(II) ions in a triazol based spin crossover complex within the thermal hysteresis loop
2009
Abstract We have investigated the effect of short laser pulses (532 nm, 4 ns, −2 ) on the spin state of iron(II) ions in the spin crossover compound {[Fe II (Htrz) 2 (trz)](BF 4 )} within the hysteresis region of the high-spin (HS) to low-spin (LS) first-order thermal phase transition. Using Raman spectroscopy we have evidenced quasi-complete HS → LS as well as LS → HS photo-conversions, which can be induced by a single laser shot in the descending (351 K) and ascending (378 K) branches of the hysteresis loop, respectively. No effect has been observed, however, close to the center of the hysteresis loop even for repeated exposures.
Experimental Realization of a Dirac Monopole through the Decay of an Isolated Monopole
2017
We experimentally observe the decay dynamics of deterministically created isolated monopoles in spin-1 Bose-Einstein condensates. As the condensate undergoes a change between magnetic phases, the isolated monopole gradually evolves into a spin configuration hosting a Dirac monopole in its synthetic magnetic field. We characterize in detail the Dirac monopole by measuring the particle densities of the spin states projected along different quantization axes. Importantly, we observe the spontaneous emergence of nodal lines in the condensate density that accompany the Dirac monopole. We also demonstrate that the monopole decay accelerates in weaker magnetic field gradients.
High-Spin → Low-Spin Relaxation in [Fe(bpp)2](CF3SO3)2 H2O after LIESST and Thermal Spin-State Trapping—Dynamics of Spin Transition Versus Dynamics o…
1996
The iron(II) complex [Fe(bpp)2]-(CF3SO3)2 H2O (bpp = 2,6-bis(pyrazolyl-3-yl)pyridine) shows a thermal spin transition associated with a hysteresis of approximately 140 K width. The transition temperatures T1/2 (where the fraction of HS species γHS = 0.5) are 147 K and ≈285 K in the cooling and heating directions, respectively. The compound shows the LIESST and reverse-LIESST effects at low temperatures. The relaxation of the metastable HS states generated by LIESST was observed quantitatively at temperatures between 77.5 and 85 K by Mossbauer spectroscopy. Metastable HS states can also be generated by rapid cooling of the sample. The relaxation of the metastable HS states formed by thermal …
Insights on the coupling between vibronically active molecular vibrations and lattice phonons in molecular nanomagnets
2021
Spin-lattice relaxation is a key open problem to understand the spin dynamics of single-molecule magnets and molecular spin qubits. While modelling the coupling between spin states and local vibrations allows to determine the more relevant molecular vibrations for spin relaxation, this is not sufficient to explain how energy is dissipated towards the thermal bath. Herein, we employ a simple and efficient model to examine the coupling of local vibrational modes with long-wavelength longitudinal and transverse phonons in the clock-like spin qubit [Ho(W$_5$O$_{18}$)$_2$]$^{9-}$. We find that in crystals of this polyoxometalate the vibrational mode previously found to be vibronically active at …
Light-Induced Excited Spin State Trapping in Iron(II) Complexes
1987
In the course of our studies on the thermally induced high spin (HS) ↔ low spin (LS) transition in iron(II) complexes /1/, \({\!^5{\text{T}}_2}_{\text{g}}\) ↔ \({\!^1{\text{A}}_1}_{\text{g}}\) in the approximation of Oh symmetry, we have observed in 1984 a new photophysical effect /2/: If, at sufficiently low temperature, the solid spin crossover complex is irradiated with green light into the \({\!^1{\text{A}}_1}\)→ \({\!^1{\text{T}}_1}\) ligand field absorption band, the thermodynamically stable LS state can be converted to the metastable HS state and trapped with practically infinite lifetime. We have called this unusual phenomenon “Light-Induced Excited Spin State Trapping (LIESST)”.
Transport anisotropy and of thin films
2005
Abstract The resistivity R ( T ) of superconducting UNi 2 Al 3 thin films shows a pronounced dependence on the current direction. Specifically, the superconducting transition temperature T c is directional dependent as well as the influence of the magnetic ordering on the transport properties. Also the upper critical field B c 2 ( Θ , T ) is moderately influenced by the probe current direction. These anisotropies are discussed in the framework of multiband superconductivity. The initial slope of the upper critical field B c 2 ′ ( T ) provides evidence for a spin singlet state.
A heterobimetallic [MnII5CuII5] nanowheel modulated by a flexible bis-oxamate type ligand
2015
The synthesis, crystal structure and preliminary magnetic characterization of a new heterobimetallic [MnII5CuII5] wheel containing a flexible bis-oxamate type ligand are described. This decanuclear compound exhibits a relatively strong intra-wheel antiferromagnetic interaction leading to a ground spin state S = 10.