Spin state dependence of electrical conductivity of spin crossover materials

We studied the spin state dependence of the electrical conductivity of the spin crossover compound [Fe(Htrz)2(trz)](BF4) (Htrz = 1H-1,2,4-triazole) by means of dc electrical measurements. The low spin state is characterized by higher conductance and lower thermal activation energy of the conductivity, when compared to the high spin state

Electrical properties and non-volatile memory effect of the [Fe(HB(pz)3)2] spin crossover complex integrated in a microelectrode device

We report on the deposition of thin films of the [Fe(HB(pz)3)2] (pz = pyrazolyl) molecular spin crossover complex by thermal evaporation. By means of impedance measurements and Raman microspectroscopy, we show that the films maintain the structure and properties of the bulk material. The conductivity of the films decreases by ca. 2 orders of magnitude when the freshly deposited compound goes through a first (irreversible) thermal phase change above ca. 380 K. This property can be exploited as a non-volatile (read-only) memory effect

Nano-electromanipulation of Spin Crossover Nanorods: Towards Switchable Nanoelectronic Devices

The nanoscale manipulation and charge transport properties of the [Fe(Htrz)2(trz)](BF4) spin-crossover compound is demonstrated. Such 1D spin-crossover nanostructures are attractive building blocks for nanoelectronic switching and memory devices

Effect of ligand substitution in [Fe(H-trz)2(trz)]BF4 spin crossover nanoparticles

Spin crossover iron(II) 1,2,4-triazole-based coordination compounds in the form of nanoparticles were prepared using a reverse microemulsion technique. Ligand substitution approach was applied to decrease the spin crossover temperature towards room temperature in the well-known [Fe(Htrz)2(trz)]BF4 complex. The compositions of the particles were determined by elemental analysis and thermogravimetry. The morphology was monitored by transition electron microscopy (TEM). The effect associated with the ligand substitution was investigated by optical and magnetic measurements. Transition temperature has been reduced by 33 K comparing the unsubstituted sample to that with 5 % substitution

Charge Transport and Electrical Properties of Spin Crossover Materials: Towards Nanoelectronic and Spintronic Devices

In this paper, we present a comprehensive review of research on electrical and charge transport properties of spin crossover complexes. This includes both the effect of spin-state switching on the dielectric permittivity and electrical conductivity of the material and vice versa the influence of an applied electrical field (or current) on the spin-state of the system. The survey covers different size scales from bulk materials and thin films to nanoparticles and single molecules and embraces the presentation of several device prototypes and hybrid materials as well

Active Based-Metasurfaces for Mid-Infrared Optoelectronics Devices

We develop low-temperature (450°C) deposition conditions for vanadium di-oxide phase change material. It permits implementation of tunable mid-infrared meta-surfaces on quantum cascade lasers based heterostructures

Gigantic terahertz magnetochromism via electromagnons in hexaferrite magnet Ba2_2Mg2_2Fe12_{12}O22_{22}

Effects of temperature (6--225 K) and magnetic field (0--7 T) on the low-energy (1.2--5 meV) electrodynamics of the electromagnon, the magnetic resonance driven by the light electric field, have been investigated for a hexaferrite magnet Ba$_2$Mg$_2$Fe$_{12}$O$_{22}$ by using terahertz time-domain spectroscopy. We find the gigantic terahertz magnetochromism via electromagnons; the magnetochromic change, as defined by the difference of the absorption intensity with and without magnetic field, exceeds 500% even at 0.6 T. The results arise from the fact that the spectral intensity of the electromagnon critically depends on the magnetic structure. With changing the conical spin structures in terms of the conical angle $\theta$ from the proper screw ($\theta=0^\circ$) to the ferrimagnetic ($\theta=90^\circ$) through the conical spin-ordered phases ($0^\circ<\theta<90^\circ$) by external magnetic fields, we identify the maximal magnetochromism around $\theta\approx45^\circ$. On the contrary, there is no remarkable signature of the electromagnon in the proper screw and spin-collinear (ferrimagnetic) phases, clearly indicating the important role of the conical spin order to produce the magnetically-controllable electromagnons. The possible origin of this electromagnon is argued in terms of the exchange-striction mechanism.Comment: 19 pages including 7 figures; Accepted for publication in Phys. Rev.