Conductance fluctuations in cobalt valence tautomer molecular thin films
The bistability and the conductivity changes associated with optical excitations in cobalt valence tautomer molecular thin films were investigated.
Phillips, Jared P.↗
Engineering topics
Mishra, Esha
Publications and source records attributed to Mishra, Esha.
Electronic transport and polarization-dependent photoresponse in few-layered hafnium trisulfide (HfS 3 ) nanoribbons
Few-layered HfS 3 nanoribbons exhibit n-type conductivity and a large photoresponse to visible light. The photocurrent strongly depends on the polarization direction of the excitation laser due to the highly anisotropic quasi-1D crystal structure of HfS 3 .
Lipatov, Alexey↗
Electronic structure of cobalt valence tautomeric molecules in different environments
A joint spectroscopy and ab initio study identifies electronic orbitals of valence tautomeric complexes on different semiconducting polymers, including a spin-polarized ligand-to-metal charge transfer state that spans the entire molecular plane.
Mishra, Esha↗
Perturbing the spin state and conduction of Fe (II) spin crossover complexes with TCNQ
In this study, we investigated modifications driven by 7,7,8,8-tetracyanoquinodimethane (TCNQ) to the spin state configuration of [Fe(3-bpp) 2 ](TCNQ) 2 co-crystal and both spin state and electric conductivity of [Fe{H 2 B(pz) 2 } 2 (bipy)] and TCNQ mixtures. The Fe 2+ site in the [Fe(3-bpp) 2 ](TCNQ) 2 co-crystal has a sizable orbital moment. During X-ray absorption measurements, the iron ion is partially excited to the high spin state and strong surface effects are indicated. Mixing TCNQ with the [Fe{H 2 B(pz) 2 } 2 (bipy)] spin crossover complex leads to a molecular combination with increased conductivity and drift carrier lifetimes. [Fe{H 2 B(pz) 2 } 2 (bipy)] thin films with TCNQ, grown using dimethylformamide (DMF), are to great extent locked mainly in the low spin (LS) state across a broad temperature range and exhibit drift carrier lifetimes approaching 0.5 s. When deposited onto a ferroelectric polyvinylidenefluoride-hexafluoropropylene thin film substrate, [Fe{H 2 B(pz) 2 } 2 (bipy)], shows enhanced transistor carrier mobility, likely associated with the increasing cationic character of [Fe{H 2 B(pz) 2 } 2 (bipy)] thin films with TCNQ.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Evidence of dynamical effects and critical field in a cobalt spin crossover complex
The [Co(SQ) 2 (4-CN-py) 2 ] complex exhibits dynamical effects over a wide range of temperature. Additionally, the orbital moment, determined by X-ray magnetic circular dichroism (XMCD) with decreasing applied magnetic field, indicates a nonzero critical field for net alignment of magnetic moments, an effect not seen with the spin moment of [Co(SQ) 2 (4-CN-py) 2 ].
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Magnetic moments and spin structure in single-phase B20 Co 1+x Si 1-x (x = 0.043)
Neutron powder diffraction (NPD) and x-ray magnetic circular dichroism (XMCD) spectroscopy are employed to investigate the magnetism and spin structure in single-phase B20 Co 1.043 Si 0.957 . The magnetic contributions to the NPD data measured in zero fields are consistent with the helical order among the allowed spin structures derived from group theory. The magnitude of the magnetic moment is (0.3 ± 0.1) μ B /Co according to NPD, while the surface magnetization probed by XMCD at 3 kOe is (0.18–0.31) μ B /Co. Both values are substantially larger than the bulk magnetization of 0.11 μ B /Co determined from magnetometry at 70 kOe and 2 K. Finally, these experimental data indicate the formation of a helical spin phase and the associated conical states in high magnetic fields.
36 MATERIALS SCIENCE↗
Evidence for surface effects on the intermolecular interactions in Fe( ii ) spin crossover coordination polymers
From X-ray absorption spectroscopy (XAS) and X-ray photoemission spectroscopy (XPS) it is evident that the spin state transition behavior of Fe( ii ) spin crossover coordination polymer crystallites at the surface differs from the bulk.
Ekanayaka, Thilini K.↗
Magnetic Field Perturbations to a Soft X-ray-Activated Fe (II) Molecular Spin State Transition
The X-ray-induced spin crossover transition of an Fe (II) molecular thin film in the presence and absence of a magnetic field has been investigated. The thermal activation energy barrier in the soft X-ray activation of the spin crossover transition for [Fe{H2B(pz)2}2(bipy)] molecular thin films is reduced in the presence of an applied magnetic field, as measured through X-ray absorption spectroscopy at various temperatures. The influence of a 1.8 T magnetic field is sufficient to cause deviations from the expected exponential spin state transition behavior which is measured in the field free case. We find that orbital moment diminishes with increasing temperature, relative to the spin moment in the vicinity of room temperature.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Probing the unpaired Fe spins across the spin crossover of a coordination polymer
For the spin crossover coordination polymer [Fe(L1)(bipy)] n (where L1 is a N 2 O 2 2− coordinating Schiff base-like ligand bearing a phenazine fluorophore and bipy = 4,4′-bipyridine), there is compelling additional evidence of a spin state transition.
Ekanayaka, Thilini K.↗