Spin transition properties of metal (Zn, Mn) diluted Fe(phen)2(NCS)2 spin-crossover thin films

We report here the effect of metal (Zn and Mn) dilution on the spin transition of Fe(phen)2(NCS)2 thin film spin-crossover (SCO) complex. The SCO complexes are deposited on glass and indium-tin-oxide (ITO) coated glass by dip-coating technique. The growth of the films is clearly confirmed by the appearance of the sharp optical absorption band at 521–540 nm corresponding to 1A1g to 1T1g ligand field absorption of the SCO complex. Although the microstructure of the films remains unaffected by metal dilution, substitution of Fe(II) by either Zn(II) (diamagnetic) or Mn(II) (paramagnetic) results in subtle changes in the bonding environment of the host metal as inferred form X-ray diffraction and Raman studies. The high spin to low spin (or vice versa) transition can be triggered either by electric field or magnetic field as revealed in the measured current (I)–voltage (V) profile or magnetization data of the films. The data further shows the effect of metal dilution on the spin transition temperatures(T1/2), produced hysteresis loop width and loop area, which are the crucial parameter for fabricating spin-based room temperature switching devices.

Compensation effects and relation between the activation energy of spin transition and the hysteresis loop width for an iron(ii) complex

Wide thermal hysteresis loops for iron(ii) spin crossover complexes are associated with high activation barriers: the higher the activation barrier, the wider the hysteresis loop for a series of related spin crossover systems.

Facile Solution-Grown Mo-Doped Vanadium Dioxide Thermochromic Films with Decreased Phase Transition Temperature and Narrowed Hysteresis Loop Width

Molybdenum (Mo) doped vanadium dioxide (VO2) (V1-xMoxO2) thermochromic thin films with different Mo concentrations on borosilicate glasses were successfully synthesized via a facile and economic solution-based deposition method. The influences of substitutional doping with Mo dopants on the crystal structure and film morphology of VO2 were evaluated. All of the films were confirmed to be pure monoclinic crystalline phase of VO2 and no molybdenum oxides formed, suggesting the formation of a homogeneously dispersed solid-solution. The particle sizes and root-mean-square (RMS) roughness level obviously decreased upon Mo doping. V1-xMoxO2 films exhibited low metal-semiconductor transition (MST) temperature (Tc) and retained the excellent switching property at near-infrared region simultaneously. The rate of change of Tc with Mo doping reached as high as ~10°C/at.%. The reduced Tc may be attributed to the disruption of homo-polar V4+-V4+ bonding after the incorporation of Mo atoms in VO2 octahedron configuration. V1-xMoxO2 thin films exhibited narrower hysteresis loop width compared to undoped VO2, which show the promise for promoting practical implementation of VO2-based thermochromic fenestration.

Hysteresis in vortex-induced vibrations: critical blockage and effect of m*

The hysteretic behaviour of a freely vibrating cylinder, near the low-Reynolds-number end of synchronization/lock-in, in the laminar regime is investigated. Computations are carried out using a stabilized finite-element method. The flow remains two-dimensional in this Reynolds number regime. This is verified via comparison of two- and three-dimensional computations. The cylinder is free to undergo crossflow as well as in-line vibrations. The combined effect of mass ratio (1 ≤ m* ≤ 100) and blockage (0.25% ≤ B ≤ 12.5%) is studied in detail. The existence of a critical mass ratio (m*cr = 10.11), below which hysteresis disappears for an unbounded flow situation, is identified. For higher mass ratio the hysteretic behaviour is observed for all blockage. However, the hysteresis loop width is found to vary with B; its variation with m* and B is studied. The concept of critical blockage Bcr is introduced. For B ≤ Bcr the response of the cylinder is virtually the same as that in an unbounded flow domain. The variation of Bcr with m* is investigated. Furthermore, Bcr is found to vary non-monotonically with m* for m* ≤ m*cr and is almost constant for m* ≥ 20. The effect of damping, as well as restricting the cylinder to undergo transverse vibrations only, on the hysteresis behaviour is studied. The transverse-only motion leads to a larger hysteresis loop width compared with the transverse and the in-line motion of the cylinder. An attempt is made to explain this by comparing the results from forced vibrations.

Synthesis and Electrical Property of VO2 (M) Nanorods

ABSTRACTVO2 (M) nanorods have been synthesized and the morphology and structure of the sample were characterized by XRD, SEM, and HRTEM. The results show that for VO2 (M) nanorods, the transition temperature is 65 °C and the hysteresis loop width is 8 °C. The active energy of low temperature semiconducting phase is 0.2eV, which indicates that its Fermi energy level situates on the middle energy level of the forbidden-band. The doping of Mo6+ decreases its transition temperature.