Optical, dielectric and magnetic properties of Mn doped SnO2 diluted magnetic semiconductors (original) (raw)
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SnO 2 doped with Mn, Fe or Co: room temperature dilute magnetic semiconductors
Room temperature ferromagnetism is found in (Sn 1Ϫx M x )O 2 (M ϭMn, Fe, Co, xϭ0.05) ceramics where x-ray diffraction confirms the formation of a rutile-structure phase. Room temperature saturation magnetization of 0.2 and 1.8 Am 2 kg Ϫ1 for (Sn 0.95 Mn 0.05 )O 2 and (Sn 0.95 Fe 0.05 )O 2 , respectively, corresponds to a moment of 0.11 or 0.95 B per Mn or Fe atom. The Curie temperatures are 340 and 360 K, respectively. The magnetization cannot be attributed to any identified impurity phase. 57 Fe Mössbauer spectra of the Fe-doped SnO 2 samples, recorded at room temperature and 16 K, show that about 85% of the iron is in a magnetically ordered high spin Fe 3ϩ state, the remainder being paramagnetic.
Room temperature variation in dielectric and electrical properties of Mn doped SnO 2 nanoparticles
Materials Today: Proceedings, 2017
Pure and Mn doped SnO 2 nanoparticles of the composition Mn x Sn (1-x) O 2 where (x = 0.0, 0.03, 0.05, 0.07) were synthesized by sol gel auto combustion method. Structural studies performed by XRD and EDS suggest that the crystal system remains pure rutile with a tetragonal structure even after the doping of Mn. The EDS analysis reveals that both Sn and Mn elements are present in the sample which confirmed the successful doping of Mn in the SnO 2 host structure. The identification of the various chemical bonds present in the pure and Mn doped samples has been carried out through Fourier Transform Infrared spectroscopy. FTIR spectrum has been recorded in solid phase using KBr pellets technique in the regions of 4000-400 cm-1. The complex dielectric constant, complex impedance, and a.c. conductivity have been studied as function of frequency and composition using LCR meter. Dielectric constant and loss was found to decrease with the increase in frequency and the obtained results have been explained on the basis of Maxwell-Wagner model. A.C. conductivity was found to increase with the increase in frequency due to hopping between charge carriers. It increases with the increase in dopant level which may be due to the free electron density and crystalline size.
Nanoparticles samples of pure SnO 2 , Sn 0. were synthesized by sol-gel method. X-ray diffraction analysis and Fourier transform infrared spectra of all prepared samples confirmed the formation of single phase SnO 2 with tetragonal rutile structure. The average crystallite sizes of the prepared samples were estimated to be in the range of 7-12 nm. Energy-dispersive X-ray spectroscopy analysis of Sn 0.98 Mn 0.02 O 2 , Sn 0.96 Mn 0.02 Fe 0.02 O 2 , and Sn 0.96 Mn 0.02 Co 0.02 O 2 samples evidently proved the existence of Mn, Fe, Co, Sn, and O elements only without any impurity, indicating the high purity of the prepared samples. Transmission electron microscopy images showed the formation of ultra-fine spherical nano-particles in all samples with average particles sizes of 8.5-15 nm. From the UV-Vis absorption spectra results, the band gap energy value of the pure SnO 2 nanoparticles was estimated to be 3.90 eV and it varied with dopant type and its concentration. Room temperature magnetic hysteresis loops of all samples exhibited ferromagnetic behavior. Clear enhancement in the room temperature ferromagnetism was achieved in pure SnO 2 nanoparticles after doping with Mn and codoping with (Mn, Fe) or (Mn, Co) dopants. The maximum value of the saturation magnetization was found in Sn 0.96 Mn 0.02 Fe 0.02 O sample, while Sn 0.96 Mn 0.02 Co 0.02 O sample displayed the higher values of coercivity and retentivity. Graphical Abstract
Physica B: Condensed Matter, 2019
The comprehensive investigation of Raman modes, magnetic and dielectric properties have been carried out on Mn-Co co-doped SnO 2 nanoparticles by fixing Mn content (5%) and varying doping concentration of Co (0%, 1%, 3%, and 5%). Average crystallite size estimated from Williamson Hall analysis is found to be in decreasing order on increasing concentration of Co and ranging between 29.4 nm and 19.2 nm. Transmission electron microscopy analysis gives evidence that the pre-synthesized Mn-Co co-doped SnO 2 powder samples contain nanoparticles with particle size 24.5 nm for 5% Mn doped SnO 2 and 14.5 nm for 5% Mn + 5% Co co-doped SnO 2. These nanoparticles exhibit a very strange ferromagnetic to superparamagnetic transition and superparamagnetic phase of the samples grows on increasing Co content. This improved superparamagnetic phase in Mn-Co codoped SnO 2 nanoparticles may offer ferrofluids and several biomedical applications like MRI, drugs delivery, hyperthermia, etc. The origin of electric polarization in the Mn-Co co-doped SnO 2 nanoparticles has been explained on the basis of dielectric permittivity and typical dielectric dispersion. The small polaron hopping and correlated barrier hopping was found as a dominating ac conduction mechanism in 5% Mn doped SnO 2 and heavily co-doped (5% Mn + 5% Co) SnO 2. The typical behavior of increasing ac activation energy in Mn-Co codoped SnO 2 samples with frequencies have also been depicted.
High temperature ferromagnetism in Mn-doped SnO2 nanocrystalline thin films
Journal of Applied Physics, 2007
It has been possible to induce room temperature ferromagnetism, exhibiting high transition temperature, in tin oxide thin films by introducing manganese in a SnO2 lattice. The observed temperature dependence of the magnetization predicts a Curie temperature exceeding 550 K. A maximum saturation magnetic moment of 0.18+/-0.04 μB per Mn ion has been estimated for spray pyrolized Sn1-xMnxO2-δ thin films, with x=0.10. For Mn concentration (x) higher than 0.10, the films show linear behavior. The magnetization-versus-field studies indicate that the origin of ferromagnetism lies neither in ferromagnetic metal clusters nor in the presence of metastable phases. The structure factor calculations reveal that Mn has been incorporated in the SnO2 lattice. Also, the electron transport investigation indicates that there is a change of Mn occupancy from substitutional to interstitial sites of the SnO2 lattice when the Mn concentration exceeds 7.5 at. %. These films do not exhibit anomalous Hall effects at room temperature. The optical absorption study indicates that the Sn1-xMnxO2-δ system behaves like a random alloy. The generation of additional free electrons by F doping in Sn0.90Mn0.10O2-δ thin films does not cause any increase in the magnetic moment per Mn ion, suggesting no significant role of electrons in bringing about the magnetic ordering.
A study on structural and optical properties of Mn- and Co-doped SnO2 nanocrystallites
Materials Chemistry and Physics, 2010
Pure and transition metal ion (Mn and Co)-doped SnO 2 nanoparticles were synthesized using a simple chemical precipitation method. Transition metal ions (Mn and Co) of 1, 3 and 5 mol% were doped in order to study the influence of structural and optical properties. The structural, chemical and optical properties of the samples were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, and UV-vis spectroscopy techniques. The SnO 2 crystallites were found to exhibit tetragonal rutile structure with lattice parameters, revealing that the metal ions get substituted in the SnO 2 lattice. It is observed that the peak position (1 1 0) get shifted to lower angles by increasing the dopant concentration. Hence the lattice parameters (a and c) and the cell volume get decreased. The SEM photograph shows that the grain size of pure SnO 2 is larger than that of the metal-doped SnO 2 indicating grain growth upon doping. TEM photograph revels that by increasing the content of metal ions, average grain size decreased. A significant red shift in the UV absorbing band edge was observed with the increase in the amount of the Mn and Co contents.
2017
Mn and Mn-Co doped SnO 2 have been successfully synthesized using co-precipitation technique. The structural properties and surface morphology were studied using x-ray diffractometer (XRD) and scanning electron microscopy (SEM) respectively. Composition analysis of the samples has been carried out from EDX data. Optical properties were studied using reflectance spectroscopy in the wavelength range 200 nm-800 nm and IR absorption spectroscopy in the wave number range 400 cm À1 e4000 cm À1. Reflectance spectra revealed that the band gap of prepared samples changes with doping concentration and found to be in the range 3.91 eVe3.95 eV. Infrared (IR) absorption spectra describe the different mode of band related to a functional group present in the materials. Mn and Mn-Co doped SnO 2 exhibit very strong emission near the wavelength 413 nm and 434 nm. DC resistivity measurement shows that the activation energy increases with increasing concentration of dopant.
Pure and Indium (In) doped SnO2 nanocrystalline thin films have been fabricated using sol-gel technique. The effect of In-doping on structural, optical and magnetic properties has been studied. Scanning electron microscopy (SEM) study reveals that the grains of pure and doped SnO2 possesses spherical symmetry. X-ray diffraction (XRD) study reveals that pure and In-doped SnO2 thin films possess rutile structure having tetragonal phase. UV-visible study suggests that with In-doping in SnO2, the value of the band gap first increases (upto 5% In-concentration) but further increase in concentration of In to 25% leads to decrease in band gap. It has been found from the room temperature magnetic study that pure and In-doped SnO2 thin films show ferromagnetic behaviour, however with 5% In-doping saturation magnetization value increased. The observed ferromagnetic behaviour may be due to the defects and oxygen vacancies.
Magnetic properties of (Mn, Al) doped SnO2 nanoparticles: synthesis and characterization
Journal of Materials Science: Materials in Electronics, 2021
Pure and (Mn, Al) co-doped SnO2 nanoparticles were synthesized using co-precipitation method. Different concentrations of Mn (1, 3, 5 mol%) were doped into SnO2 at 5 mol% constant concentration of Al. The X-ray diffraction (XRD) studies revealed the formation of single tetragonal rutile-type phase in pure and (Mn, Al) doped SnO2 nanoparticles. The particle sizes were in the range of 20–30 nm, as calculated from the XRD data. Raman studies revealed that the pure and (Mn, Al) doped SnO2 nanoparticles have active modes at 150 (B1g), 306 (Eu), 476 (Eg), 625 (A1g) and 776 cm−1 (B2g) corresponding to tetragonal rutile-type phase SnO2. The SEM micrographs show that the surface morphology of samples was formed by non-uniform spherical in shape particles. The chemical composition of samples was analyzed by EDAX spectra analysis. The presence of Sn4+, Al3+, O−2 and Mn2+ ions was confirmed in the prepared samples. The observation of TEM micrographs confirmed the non-uniform spherical shape sur...
High temperature ferromagnetism in Mn-doped SnO[sub 2] nanocrystalline thin films
Journal of Applied Physics, 2007
It has been possible to induce room temperature ferromagnetism, exhibiting high transition temperature, in tin oxide thin films by introducing manganese in a SnO 2 lattice. The observed temperature dependence of the magnetization predicts a Curie temperature exceeding 550 K. A maximum saturation magnetic moment of 0.18± 0.04 B per Mn ion has been estimated for spray pyrolized Sn 1−x Mn x O 2−␦ thin films, with x = 0.10. For Mn concentration ͑x͒ higher than 0.10, the films show linear behavior. The magnetization-versus-field studies indicate that the origin of ferromagnetism lies neither in ferromagnetic metal clusters nor in the presence of metastable phases. The structure factor calculations reveal that Mn has been incorporated in the SnO 2 lattice. Also, the electron transport investigation indicates that there is a change of Mn occupancy from substitutional to interstitial sites of the SnO 2 lattice when the Mn concentration exceeds 7.5 at. %. These films do not exhibit anomalous Hall effects at room temperature. The optical absorption study indicates that the Sn 1−x Mn x O 2−␦ system behaves like a random alloy. The generation of additional free electrons by F doping in Sn 0.90 Mn 0.10 O 2−␦ thin films does not cause any increase in the magnetic moment per Mn ion, suggesting no significant role of electrons in bringing about the magnetic ordering.