Search query: Crystallographic properties of I2–Fe–iv–vi4 magnetic semiconductor compounds

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abstract: X ray powder diffraction measurements were made at room temperature on sixteen polycrystalline samples of I{sub 2} Fe IV VI{sub 4} (I: Cu, Ag; IV: Si, Ge, Sn, Pb; VI: Se, Te) magnetic semiconductor compounds. The diffraction patterns were analyzed to determine values of lattice parameter for each compound. The results showed that Cu{sub 2}FeSiSe{sub 4} Cu{sub 2}FeGeSe{sub 4} and Cu{sub 2}FeSnSe{sub 4} have the tetragonal stannite structure (I{bar 4}2m) while the rest of the materials have an orthorhombic superstructure of quartzite which is known as wurtz stannite (Pmn2{sub 1} It was found that, when the values of the effective parameter a{sub e} (V/N){sup 1/3} are plotted against the molecular weight W of the materials, the tetragonal and orthorhombic compounds lie on different straight lines. In addition, differential thermal analysis (DTA) measurements were made, and the peaks on the DTA cooling curves were used to determine values corresponding to the melting temperature for the compounds.
author_names: Maritza Quintero

A Barreto

P Grima

Rafael Giner Tovar

Eugenio Quintero

G Sanchez Porras

J Ruiz

John C Woolley

Gilles Lamarche

A -M Lamarche
title: Crystallographic properties of I2 Fe iv vi4 magnetic semiconductor compounds
year: 1999

abstract: The inclusion of several cations in the A and B crystallographic sites of the A 4 x A' x B 4 y z B' y B' z O 12 complex perovskite gives rise to diverse physical properties, depending on the constituent elements of the material. In this work, structural, morphological, compositional, magnetic and electric characterization of the solid reacted compound Nd 2.68 Sr 1.32 Mn 1.2 Ti 1.32 Fe 1.48 O 12 is reported. Rietveld analysis of X ray diffraction data revealed that this material crystallizes in an orthorhombic perovskite structure Pnma, #62 space group) The surface morphologic study showed the formation of polycrystalline material with diverse shape of grains of 1.50 mm mean size. Compositional characterization through the energy dispersive X ray spectroscopy technique suggests that there are no other elements in the material besides the expected Nd, Sr, Mn, Ti, Fe and O, which are present in percentage proportions very close to the expected values from the material stoichiometry. E J curves exhibit hysteretic features which are typical of the thermistor like materials. Electric resistivity as a function of temperature showed an Arrhenius behavior also observed in doped semiconductors. Diffuse reflectance spectra revealed an optical band gap of 1.17 eV. Magnetic susceptibility measurements as a function of temperature evidenced a ferrimagnetic response, and hysteretic curves of magnetization at T 50 K, 200 K and 300 K corroborated the occurrence of magnetic ordering, which permit to classify this material as a ferrimagnetic semiconductor with potential applicability in the spintronic device industry at room temperature.
author_names: Javier Farfan

J P Benavides Lara

Carlos A Parra Vargas

David A Landinez Tellez

Jairo Roa-Rojas
title: Structural Characteristics and Electric and Magnetic Features of the Nd2.68Sr1.32Mn1.2Ti1.32Fe1.48O12 Ferromagnetic Semiconductor
year: 2020

abstract: Abstract We synthesized and characterized the non peripherally and peripherally tetra substituted manganese (III) phthalocyanines (3) and (4) containing [4 (2 methoxyethyl)phenoxy] group. Synthesized compounds were characterized by standard spectroscopy methods. The crystallographic information and stabilization dynamics of supramolecular structure of intended compound (2) have been revealed by the analysis of single crystal X ray diffraction measurements. The optical, sensing, conductance and electrical properties were investigated. The absorption band edge values of the MnIIIClPc (3) are lower than that of the MnIIIClPc (4) The optical band gaps of the MnIIIClPc (3) and MnIIIClPc (4) display direct allowed optical band gap and semiconductor behaviour. The refractive indices of the functional manganese(III) phthalocyanine compounds give significant results for preparation of diodes and sensor devices. The surface morphological properties of the MnIIIClPc (3) and (4) films were investigated under different conditions. Finally, quantum chemical parameters of the synthesized compounds were calculated using quantum chemical calculations. The calculated Infrared spectroscopy, Nuclear Magnetic Resonance, and UV Vis spectra of all compounds were investigated and the obtained parameters were compared with experimental values.
author_names: Armagan Gunsel

Ahmet T Bilgicli

Hasan Piskin

Burak Tuzun

Nagihan Caylak Delibas

M Nilufer Yarasir

Bayram Gunduz
title: Comparison of spectroscopic, electronic, theoretical, optical and surface morphological properties of functional manganese(III) phthalocyanine compounds for various conditions
venue: Journal of Molecular Structure
year: 2019

abstract: Epitaxial growth and magnetic properties of group IV ferromagnetic semiconductor Ge1 xFex thin films were investigated by employing in situ reflection high energy electron diffraction (RHEED) transmission electron microscopy (TEM) and magnetic circular dichroism (MCD) When Ge1 xFex films were grown at substrate temperatures (TS) of 100 200 degC, their RHEED pattern showed streaks with a 2x2 reconstruction pattern, indicating two dimensional growth mode with atomically flat surface morphology. Single phase crystallographic structure without Fe Ge intermetallic compounds was observed in the films by TEM. MCD measurements revealed that s,p d exchange interactions induced by the incorporation of Fe atoms that occupied the substitutional sites of the host Ge matrix cause single phase ferromagnetic ordering in the Ge1 xFex films. Above TS 300 degC, the growth mode was changed from two dimensional growth mode to three dimensional growth mode. It was found from MCD observations that when Ge1 xFex films are grown at TS 300 400 degC, phase separation occurs and the films contain ferromagnetic precipitates. A ferromagnetic semiconductor phase was obtained for TS ranging from 100 degC to 200 degC, and higher Curie temperature was obtained for TS 200 degC. (c) 2006 WILEY VCH Verlag GmbH Co. KGaA, Weinheim)
author_names: Yusuke Shuto

Masaaki Tanaka

Satoshi Sugahara
title: Epitaxial growth and magnetic properties of a new group IV ferromagnetic semiconductor Ge1 xFex
year: 2006

abstract: X ray powder diffraction measurements, at room temperature, and magnetic susceptibility measurements, in the temperature range from 2 to 300 K, were made on polycrystalline samples of Cu2FeGeSe4 and Cu2FeGeTe4 magnetic semiconductor compounds. Magnetization measurements at 2, 4.2 and 77 K in magnetic fields up to 35 T were carried out on Cu2FeGeSe4 compounds. From the analysis of the X ray diffraction lines, it was found that Cu2FeGeSe4 and Cu2FeGeTe4 have, respectively, stannite and monoclinic structures. The resulting 1/X versus T curves showed that Cu2FeGeSe4 is antiferromagnetic with a Neel temperature T N 20 K while Cu2FeGeTe4 is ferrimagnetic with T N 160.1 K. The magnetization and susceptibility results obtained on Cu2FeGeSe4 showed the presence of bound magnetic polarons (BMPs) in agreement with earlier studies made on this type of materials [1, 2]
author_names: Miguel Quintero

Rafael Giner Tovar

A Barreto

Eugenio Quintero

A J Rivero

J Gonzalez

G Sanchez Porras

J Ruiz

Pablo Bocaranda

J M Broto

H Rakoto

Regis Barbaste
title: Crystallographic and Magnetic Properties of Cu2FeGeSe4 and Cu2FeGeTe4 Compounds
year: 1998

abstract: We report the synthesis and basic properties of the binary compound Yb5Si4. In this compound, Yb ions occupy three different crystallographic sites, the multiplicity of which is represented by Yb1 Yb2 Yb3 1:2:2. The estimated effective magnetic moment and magnetic entropy can be explained by the proportion of Yb valence states, Yb3+ Yb2+ 2:3. This result suggests the possibility that Yb3+ ions occupy either Yb2 or Yb3 site. Yb5Si4 undergoes an antiferromagnetic transition at TN 1.7 K. The extended high temperature tail in the temperature dependence of the specific heat just above TN has been observed. Yb5Si4 also exhibits the broad maximum peak around 2.3 K in the magnetic susceptibility, corresponding to the specific heat anomaly. We propose that these anomalies are possible to originate from magnetic fluctuations caused by low dimensional Yb3+ networks. Electrical resistivity measurements on Yb5Si4 reveal semiconducting behavior at all temperatures. The small energy gap D 430 K has been obtained at room temperature estimated by the thermal activation model. The energy gap gradually decreases with decreasing temperature, and reaches about 3 K at low temperatures.
author_names: Masashi Kosaka

Shingo Ottomo

Ayumi Machida

Tomoyuki Kirigane

Ryosuke Numakura

Susumu Katano

Shinji Michimura
title: Magnetic and transport properties of the narrow gap semiconductor Yb5Si4
year: 2015

abstract: X ray diffraction measurements on MnGa2Se4, a II III2 VI4 magnetic semiconductor compound, are made as a function of pressure up to 25GPa. It is found that in the range of 0<P<12GPa the structure is a defect tetragonal; in the range between 12 and 14GPa a two phase field a+NaCl type exists. It is found that at about 14GPa a transition to the cubic NaCl type structure occurs and it appeared that this transition is irreversible. From the analysis of the x ray diffraction lines, lattice parameter values are determined as a function of pressure. These results allow the evaluation of the compressibility coefficients of the corresponding parameters. The observed behavior of d, kha, and khc with pressure are explained by using the relations proposed by Abrahams and Bernstein [J. Chem. Phys. 52, 5607 (1970) It is found that at about 3GPa, a symmetry change, from an ordered tetragonal to a disordered tetragonal structure, occurs.
author_names: Jesus Marquina

Ch Power

P Grima

Manuel Morocoima

Miguel Quintero

Bernard Couzinet

J C Chervin

Pascal Munsch

J M Gonzalez
title: Crystallographic properties of the MnGa2Se4 compound under high pressure
year: 2006

abstract: LiTi2O4 is one end member of the homogeneity range of the spinel phase Li1+xTi2 xO4 (0<=x<=1/3) and is superconducting at temperatures up to 13.7 K. Various measurements were carried out in order to characterize the superconducting and normal state properties of LiTi2O4 and of other compositions within the homogeneity range of the spinel phase. These measurements establish LiTi2O4 as ad band superconductor and show thatTc decreases to <1.5 K forx0.1. This disappearance of superconductivity with increasingx was found to be correlated with anomalous changes in the lattice parameter with composition, and, from electrical resistivity measurements, is tentatively attributed to the occurrence of a composition induced metal semiconductor transition atx0.1. The metallic character of LiTi2O4 and the composition dependence of the observed electrical properties are shown to follow from crystallographic considerations.
author_names: David C Johnston
title: Superconducting and normal state properties of Li1+xTi2 xO4 spinel compounds. I. Preparation, crystallography, superconducting properties, electrical resistivity, dielectric behavior, and magnetic susceptibility
year: 1976

abstract: Measurements of magnetization (M) at helium temperatures and with pulsed magnetic fields up to 32 T, have been made on polycrystalline samples of the three compounds Ag 2 FeGeSe 4 Ag 2 FeSiSe 4 and Cu 2 MnGeSe 4 All three compounds have orthorhombic symmetry, with the wurtz stannite structure, and have semiconductor properties. The resulting curves of M versus B have been used to give information on the magnetic spin flop and magnetic saturation transitions. The observed values of the spin flop field B f differ appreciably for the three cases, with mean values of 0.35 T for Ag 2 FeSiSe 4 4.0 T for Cu 2 MnGeSe 4 and 13.5 T for Ag 2 FeGeSe 4 The saturation behavior is also very different from one compound to another. In the case of Ag 2 FeSiSe 4 the magnetization curve at low fields 3 T) is quite different for the cases of pulsed field and steady field measurements. This is attributed to domain effects, with Ag 2 FeSiSe 4 showing weak ferromagnetic behavior because of crystallographic spin canting. This effect can also be the cause for the very low value of B f in this compound.
author_names: Miguel Quintero

R Cadenas

Rafael Giner Tovar

Eugenio Quintero

J Gonzalez

J Ruiz

John C Woolley

Gilles Lamarche

A -M Lamarche

J M Broto

H Rakoto

Regis Barbaste
title: Magnetic spin flop and magnetic saturation in Ag2FeGeSe4, Ag2FeSiSe4 and Cu2MnGeSe4 semiconductor compounds
year: 2001

abstract: Measurements of magnetization (M) at helium temperatures and with pulsed magnetic "elds up to 32 T, have been made on polycrystalline samples of the three compounds Ag FeGeSe ,A g FeSiSe and Cu MnGeSe All three compounds have orthorhombic symmetry, with the wurtz}stannite structure, and have semiconductor properties. The resulting curves of M versus B have been used to give information on the magnetic spin}#op and magnetic saturation transitions. The observed values of the spin #op "eld B di!er appreciably for the three cases, with mean values of 0.35 T for Ag FeSiSe 4.0 T for Cu MnGeSe and 13.5 T for Ag FeGeSe The saturation behavior is also very di!erent from one compound to another. In the case of Ag FeSiSe the magnetization curve at low "elds (3 T) is quite di!erent for the cases of pulsed "eld and steady "eld measurements. This is attributed to domain e!ects, with Ag FeSiSe showing weak ferromagnetic behavior because of crystallographic spin canting. This e!ect can also be the cause for the very low value of B in this compound. 2001 Elsevier Science B.V. All rights reserved.
author_names: Miguel Quintero

R Cadenas

Rafael Giner Tovar

Eugenio Quintero

J Gonzalez

J Ruiz

Gilles Lamarche

H Rakoto

Regis Barbaste
title: Magnetic spin #op and magnetic saturation in Ag FeGeSe Ag FeSiSe and Cu MnGeSe semiconductor compounds
year: 2001