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The proposed new Electron-Ion Collider poses a technical and intellectual challenge for the detector design to accommodate the long-term diverse physics goals envisaged by the program. This requires a 4{\pi} detector system capable of reconstructing the energy and momentum of final state particles with high precision. The Electron-Ion Collider also requires identification of particles of different masses over a wide momentum range. A diverse spectrum of Particle Identification detectors has been proposed. Of the four types of detectors for hadron identification, three are based on Ring Imaging Cherenkov Counter technologies, and one is realized by the Time of Flight method. The quest for a novel photocathode, sensitive in the far vacuum ultra violet wavelength range and more robust than cesium iodide, motivated an R&D programme to explore nano-diamond (ND) based photocathodes, started by a collaboration between INFN and CNR Bari and INFN Trieste. Systematic measurements of the photo emission in different Ar-CH4 and Ar-CO2 gas mixtures with various types of ND powders and Hydrogenated ND (H-ND) powders are reported. A first study of the response of THGEMs coated with different photocathode materials is presented. The progress of this R&D programme and the results obtained so far by these exploratory studies are described., Comment: arXiv admin note: substantial text overlap with arXiv:2401.17485, arXiv:2006.02352

The next generation of gaseous photon detectors is requested to overcome the limitations of the available technology, in terms of resolution and robustness. The quest for a novel photocathode, sensitive in the far vacuum ultra violet wavelength range and more robust than present ones, motivated an R&D programme to explore nanodiamond based photoconverters, which represent the most promising alternative to cesium iodine. A procedure for producing the novel photocathodes has been defined and applied on THGEMs samples. Systematic measurements of the photo emission in different Ar/CH4 and Ar/CO2 gas mixtures with various types of nanodiamond powders have been performed. A comparative study of the response of THGEMs before and after coating demonstrated their full compatibility with the novel photocathodes.

The beta Mn type Co-Zn-Mn alloys have seized significant attention due to their ability to host skyrmions at room temperature. Here we analyse the unconventional magneto-transport properties of Co8Zn8Mn4 single crystals with a Curie temperature of 275 K. A negative magnetoresistance is obtained over a wide temperature range of 50K to 300K. The deviation of the isothermal magnetoresistance (MR) curves from linearity to non-linearity as one approaches higher temperatures points towards the transition from the dominance of magnons to spin fluctuations. In the paramagnetic phase, the change in the shape of the MR curve has been explained using the Khosla and Fischer model. The relationship between the anomalous Hall effect (AHE) and longitudinal resistivity reveals the dominance of the skew-scattering mechanism, which is inexplicable based on the theories of semi-classical magneto-transport. We experimentally determine that the spin fluctuation is the source of the skew-scattering mechanism in Co8Zn8Mn4. In general skew-scattering mechanisms predominate in compounds with high conductivity, but our findings demonstrate that this is not always the case and that other aspects also require equal consideration. Our work throws new light on the predominant scattering mechanism in chiral magnets with skyrmionics phase at low conductivity.

In this manuscript, we report the results of optical properties of SnS thin films, deposited on FTO coated glass substrates at room temperature by thermal evaporation technique. In addition, the effect of film thickness on the optical behavior of FTO/SnS is analyzed and obtained results are compared with data of SnS films grown on glass and ITO substrates. Our study indicates that the properties of SnS film are independent of the substrate material. Further, the influence of the film thickness on the other optical parameters including, linear and third order nonlinear optical constants and dispersion parameters have also been investigated using the transmission, reflection, and absorption spectra. It is found that the optical band gap decreases from 2.07 to 1.30 eV with increase in SnS film thickness, whereas the refractive index increases with increasing thickness. Additionally, the oscillator energy, and the dispersion energy are estimated using WempleDiDomenico approach. The dispersion energies are in the range of 7.20 to 4.59 eV, while the oscillator energies of the thin films are in the range of 5.49 to 2.24 eV. Moreover, the nonlinear refractive index, and optical susceptibility are calculated by using the empirical relation of Tichy and Ticha. The volume of data suggests optical properties of SnS thin films are strongly dependent on film thickness., Comment: 24 pages, 11 figures

Polar magnetic oxide HoCrWO$_6$ is synthesized and its crystal structure, magnetic structure, and thermodynamic properties are investigated. HoCrWO$_6$ forms the polar crystal structure (space group Pna2$_1$ (#33)) due to the cation ordering of W$^{6+}$ and Cr$^{3+}$. There is an antiferromagnetic transition at TN = 24.5 K along with the magnetic entropy change (~5 J.Kg.$^{-1}$K$^{-1}$ at 70 kOe). Neutron diffraction measurement indicates that both Cr and Ho sublattices are ordered with the moment of 2.32(5)$\mu_B$ and 8.7(4)$\mu_B$ at 2 K, respectively. While Cr forms A-type collinear antiferromagnetic (AFM) structure with magnetic moment along the $b$ axis, Ho sublattice orders in a non-coplanar AFM arrangement. A comparison with isostructural DyFeWO$_6$ and DyCrWO$_6$ indicates that the magnetic structure of this family of compounds is controlled by the presence or absence of eg electrons in the transition metal sublattice., Comment: 7 figures, 22 pages. Journal of magnetism and magnetic materials, 2020

The present work investigates the morphological, micro-structural, compositional and fractal analysis for CsI thin films in case of "as-deposited" and "1 hour humid air aged". The variation of grain sizes obtained from transmission electron microscopy (TEM) technique are found to be in the range of ~ 313 nm to ~ 1058 nm. The average grain size is found to increase after exposing to humidity. The experimental values of interplanner spacing are found to be less than the standard value which signifies that a compressive stress is acting in the film. The elemental compositions of CsI film has been investigated by the means of energy dispersive X-ray spectroscopy (EDAX) technique. The atomic percentage of Cs:I (1:1) is found to be increased by a factor of two after exposing to humidity. The surface morphology of CsI thin films is analyzed by the atomic force microscopy (AFM) for both cases. The fractal analysis is performed on the AFM micrographs. The autocorrelation function and height-height correlation function is used to study the correlation properties of surface and roughness exponent. It is found that the fractal dimension is affected after exposing to humidity.

In this article, fractal concepts were used to explore the thermally evaporated potassium bromide thin films of different thicknesses 200, 300, and 500 nm respectively; grown on aluminium substrates at room temperature. The self-affine or self similar nature of growing surfaces was investigated by autocorrelation function and obtained results are compared with the morphological envelope method. Theoretical estimations revealed that the global surface parameters such as, interface width and lateral correlation length are monotonically decreased with increasing film thickness. Also, from height profile and A-F plots, it has been perceived that irregularity/ complexity of growing layers was significantly influenced by thickness. On the other hand, the fractal dimension and local roughness exponent, estimated by height-height correlation function, do not suggest such dependency.

In the present work, the microcrystalline characteristics of KBr thin films have been investigated by evaluating the breadth of diffraction peak. The Williamson-Hall, the Size-Strain Plot and the single line Voigt methods are employed to deconvolute the finite crystallite size and microstrain contribution from the broaden X-ray profile. The texture coefficient and dislocation density have been determined along each diffraction peak. Other relevant physical parameters such as stress, Young's modulus and energy density are also estimated using Uniform Stress-Deformation and Uniform Deformation Energy Density approximation of Williamson-Hall method.

In the present work, the morphological properties of KBr photocathodes are correlated with their photoemissive behaviour using a combination of analyzing techniques including SEM, TEM and AFM. From morphological studies, it is observed that KBr films have granular characteristics with varied average grain size and grain density. Structure and orientation of individual grains have been investigated by selected area electron diffraction technique and found to be the crystalline in nature with a face centered cubic structure. It is evident from the AFM analysis that the root mean square roughness and maximum area peak height have been decreased with the deposition of more KBr layers. The photoemission studies reveal that the resultant photocurrent is enhanced with increasing film thickness and it is directly related to the surface area coverage and grain density.

In the present work performance of cesium iodide thin film photocathode is studied in detail. The optical absorbance of cesium iodide thin films have been analyzed in the spectral range of 190 nm to 900 nm. The optical band gap energy of 500 nm thick cesium iodide film is calculated using Tauc plot from absorbance data. Refractive index is estimated from envelope plot of transmittance data using Swanepoel's method. Absolute quantum efficiency measurement has been carried out in the wavelength range of 150 nm to 200 nm. Crystallographic nature and surface morphology are investigated by X-ray diffraction, transmission electron microscopy and atomic force microscopy techniques. In addition, elemental composition result gained by energy dispersive X-ray analysis is also reported in the present work.

The performance of cesium iodide as a reflective photocathode is presented. The absolute quantum efficiency of a 500 nm thick film of cesium iodide has been measured in the wavelength range 150 nm to 200 nm. The optical absorbance has been analyzed in the wavelength range 190 nm to 900 nm and the optical band gap energy has been calculated. The dispersion properties were determined from the refractive index using an envelope plot of the transmittance data. The morphological and elemental film composition have been investigated by atomic force microscopy and X-ray photo-electron spectroscopy techniques.

We have investigated the influence of water molecule absorption on photoemissive and structural properties of potassium bromide (KBr) thin film photocathode under humid air exposure at relative humidity (RH) 65%. It is evident from photoemission measurement that the photoelectron yield of KBr photocathode is degraded exponentially with humid air exposed time. Structural studies of the "as-deposited" and "humid air aged" films reveal that there is no effect of RH on film's crystalline face centered cubic (fcc) structure. However, the average crystallite size of "humid air exposed film" KBr film has been increased as compared to "as-deposited". In addition, topographical properties of KBr film are also examined by means of scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) and it is observed that granular characteristic of film has been altered, even for short exposure to humid air.

In the present work, cesium iodide (CsI) thin films of different thickness have been prepared by thermal evaporation technique. The crystallite size and grain size of these films are compared by using X-ray diffraction (XRD) profile analysis as well as by transmission electron microscopy (TEM) counting, respectively. These two methods provide less deviation between crystallite size and grain size in the case of thin CsI films of 4 nm, but there is comparatively large difference in case of thicker CsI films (20 nm, 100 nm and 500 nm). It indicates that dislocations are arranged in a configuration which causes small orientational difference between two adjacent coherent regions. The size obtained from XRD corresponds to two separate regions, whereas in the TEM micrograph the two regions may seem to correspond one region particularly in case of thicker films. Other physical parameters such as strain, stress and deformation energy density are also estimated precisely for the prominent XRD peaks of thicker CsI films in the range $2\theta = 20^{0}-80^{0}$ by using a modified Williamson-Hall (W-H) analysis assuming uniform deformation model (UDM), uniform deformation stress model (UDSM) and uniform deformation energy density model (UDEDM)., Comment: This paper has been accepted for publication in Nuclear Inst. and Methods in Physics Research, A

Using spectroscopic ellipsometry, the refractive index and absorption versus wavelength of the ferroelectric antiferromagnet Bismuth Ferrite, BiFeO_3 is reported. The material has a direct band-gap at 442 nm wavelength (2.81 eV). Using optical second harmonic generation, the nonlinear optical coefficients were determined to be d_15/d_22 = 0.20 +/- 0.01, d_31/d_22 = 0.35 +/- 0.02, d_33/d_22 = -11.4 +/- 0.20 and |d_22| = 298.4 +/- 6.1 pm/V at a fundamental wavelength of 800 nm., Comment: 4 pages, 3 figures

We use a combination of optical spectra, first principles calculations, and energy dependent magneto-optical measurements to elucidate the electronic structure and to study the phase diagram of Ni$_3$V$_2$O$_8$. We find a remarkable interplay of magnetic field and optical properties that reveals additional high magnetic field phases and an unexpected electronic structure which we associate with the strong magneto-dielectric couplings in this material over a wide energy range. Specifically, we observed several prominent magneto-dielectric effects that derive from changes in crystal field environment around Ni spine and cross-tie centers. This effect is consistent with a field-induced modification of local structure. Symmetry-breaking effects are also evident with temperature. We find Ni$_3$V$_2$O$_8$ to be an intermediate gap, local moment band insulator. This electronic structure is particularly favorable for magneto-dielectric couplings, because the material is not subject to the spin charge separation characteristic of strongly correlated large gap Mott insulators, while at the same time remaining a magnetic insulator independent of the particular spin order and temperature., Comment: 12 figures, 11 pages, accepted in Physical Review B

We observed a large HEMD effect in the bilayer manganite (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$, a direct consequence of field driven spin-glass insulator to ferromagnetic metal transition. The remnants of the transition can be used to achieve dielectric contrast at room temperature. This discovery suggests that electronic mechanisms such as the metal-insulator transition, charge ordering, and orbital ordering can be exploited to give substantial dielectric contrast in other materials., Comment: 4 pages, 4 figures

We measured the magneto-optical response of (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$ in order to investigate the microscopic aspects of the magnetic field driven spin-glass insulator to ferromagnetic metal transition. Application of a magnetic field recovers the ferromagnetic state with an overall redshift of the electronic structure, growth of the bound carrier localization associated with ferromagnetic domains, development of a pseudogap, and softening of the Mn-O stretching and bending modes that indicate a structural change. We discuss field- and temperature-induced trends within the framework of the Tomioka-Tokura global electronic phase diagram picture and suggest that controlled disorder near a phase boundary can be used to tune the magnetodielectric response. Remnants of the spin-glass insulator to ferromagnetic metallic transition can also drive 300 K color changes in (La$_{0.4}$Pr$_{0.6}$)$_{1.2}$Sr$_{1.8}$Mn$_2$O$_7$., Comment: 9 pages, 8 figures

We report the optical and magneto-optical properties of K2V3O8, an S=1/2 quasi-two-dimensional Heisenberg antiferromagnet. Local spin density approximation electronic structure calculations are used to assign the observed excitations and analyze the field dependent features. Two large magneto-optical effects, centered at ~1.19 and 2.5 eV, are attributed to field-induced changes in the V 4+ d to d on-site excitations due to modification of the local crystal field environment of the VO5 square pyramids with applied magnetic field. Taken together, the evidence for a soft lattice, the presence of vibrational fine structure on the sharp 1.19 eV magneto-optical feature,and the fact that these optical excitations are due to transitions from a nearly pure spin polarized V d state to hybridized states involving both V and O, suggest that the magneto-dielectric effect in K2V3O8 is driven by strong lattice coupling., Comment: Zipped file containing 8 pages, 12 figures, in press PRB

We have observed a large (~1%) change in infrared reflectance of the charge-density-wave (CDW) conductor, orthorhombic TaS3, when its CDW is depinned. The change is concentrated near one current contact. Assuming that the change in reflectance is proportional to the degree of CDW polarization, we have studied the dynamics of CDW repolarization through position dependent measurements of the variation of the electro-reflectance with the frequency of square wave voltages applied to the sample, and have found that the response could be characterized as a damped harmonic oscillator with a distribution of relaxation (i.e. damping) times. The average relaxation time, which increases away from the contacts, varies with applied voltage as t0 ~ 1/V^p with p ~ 3/2, but the distribution of times broadens as the voltage approaches the depinning threshold. Very low resonant frequencies (~ 1 kHz) indicate a surprisingly large amount of inertia, which is observable in the time dependence of the change in reflectance as a polarity dependent delay of ~ 100 microsec., Comment: submitted to Phys. Rev. B