R. Murugaraj

Study of Electrical Properties in SHI Irradiated 6H‐SiC Crystals using Low Temperature Impedance Spectroscopy

In the present work, low temperature impedance measurements were made on the pristine and Ag12+ ions irradiated 6H‐SiC samples. The conductivity properties were studied at low temperature. The activation energies were calculated from the Arrhenius plot of d.c conductivity and impedance relaxation time. The activation energy was comparatively higher for the irradiated samples and found to be electronic conduction. From the study we observe the lower conductivity values exhibited for 300 K irradiated sample due to severe damage than the 80 K irradiated sample. The damage production mechanism and the change in electrical properties are discussed.

Investigations on the phase transition of Mn-doped BaTiO3 multifunctional ferroelectric ceramics through Raman, dielectric, and magnetic studies

AbstractBaTiO3 (BTO) and BaTi1−xMnxO3 (x = 0.25, 0.50, 0.75 mol%) ceramic materials have been prepared by the sol–gel combustion method. X-ray diffraction (XRD) has been carried out to characterize the phase purity and crystal structure of the prepared compounds, and all XRD patterns suggest tetragonal structure with the phase group of P4mm. The variation in the estimated lattice parameters confirms the incorporation of Mn atoms at Ti site of BTO. Raman spectroscopy studies under various temperatures suggest a phase transition from tetragonal to cubic phase at ~433 K, identified by a distinct Raman mode at 308 cm−1. As Raman modes are getting softened by Mn doping, phase transition temperature of the Mn-doped compounds is significantly decreased from 473 K (x = 0%) to 433 K (x = 0.75%). Dielectric properties such as permittivity and dielectric loss as the function of frequency under various temperatures have two distinct dielectric anomalies (i) at 393 K associated to tetragonal to cubic phase transition and (ii) at 550 K due to oxygen vacancy defect in the samples. Observation of weak ferromagnetism at 2, 300, and 400 K in the M (H) and ZFC-FC curve, suppose its origin due to an intriguing exchange interaction between Mn and oxygen vacancies. HighlightsMn-doped BaTiO3 is prepared by sol–gel combustion method.The structural phase transition from tetragonal to cubic phase occurs at ~433 K.Phase transition associated with a distinct Raman mode at ~308 cm−1.M–H loop shows weak ferromagnetism with intriguing exchange interactions.

Room temperature magnetic behaviour of Mn codoping in ZnO:Co nanoparticles synthesized by co-precipitation method

In this present work, the codoping effect of Mn2+ ions with Zn0.95Co0.05O on the structural, vibrational, morphological, optical and magnetic behaviours are reported. The Mn2+ ions codoped with Zn0.95Co0.05O nanoparticles (NPs) in steps of 0.01 are prepared by co-precipitation method. The single crystalline phase and local structure of prepared NPs were confirmed by XRD and Raman spectral analysis and Mn2+ ions codoping decreases their crystalline size and crystalline nature. The optical absorption and emissions properties of the prepared NPs were analysed using UV-DRS and PL spectroscopy techniques, respectively. The electron paramagnetic resonance (EPR) spectroscopy measurements were carried out at room temperature to reveal the presence of defects in the prepared NPs. The field dependent magnetic behaviour of prepared NPs was characterized by VSM measurements at room temperature, which confirms the room temperature ferromagnetic nature. From the Raman and Photoluminescence spectroscopy measurements, the presence of defects in prepared NPs was confirmed. The dominating role of lattice defects and grain boundary network plays a major role in magnetic behaviour was reported.

Zn interstitial defects induced magnetic nature in Fe ions doped ZnO based DMS

This paper describes the synthesis of Fe doped ZnO samples Zn{sub 1-x}Fe{sub x}0, where x various from 0.01≤x≤0.05 (in steps of 0.01) by solution method. The effect of Fe ions doping on the structural, optical and magnetic properties was investigated using X-ray diffraction (XRD), Photoluminescence and vibrating sample magnetometer (VSM) measurements. The observed result indicates that the samples are single phase formation of the wurtzite structure without any significant secondary phase in it. The photoluminescence spectra reveals the presence of Zn vacancies. The magnetic property of prepared samples was studied using a vibrating sample magnetometer and the observed results revealed a super-paramagnetic behavior for the Fe doped ZnO samples.

Structural, electrical and magnetic properties of Ni2+ substituted cobalt nanoferrite using sol-gel method

Ni doped cobalt ferrite of chemical formula Ni(1-x)CoxFe2O4 with x values = 1, 0.5, 0 were prepared by using Poly Vinyl Alcohol (PVA) sol-gel method. The prepared samples were heat treated at 450°C for an hour and grounded to form fine powder. XRD of the powder sample confirms the formation of spinel ferrite phase. SEM and EDAX spectrum reveals the surface and chemical composition of the sample. FTIR spectra of the samples show the stretching vibration of the tetrahedral (ν1) and octahedral (ν2) bands of Fe-O bonds appearing at 600cm−1 and 424cm−1 respectively. Room temperature magnetic and electrical studies were done using VSM and LCZ meter to analyze their property respectively.

Low temperature relaxation properties of SHI irradiated N-doped 6H-SiC

The low-temperature behavior of conductivity relaxation of disordered N-doped 6H-SiC is investigated. This work presents the effect of swift heavy ion (SHI) irradiation on 6H-SiC studied using impedance spectroscopy (IS). SHI irradiation was done with the fluences 8 × 1012 and 2 × 1013 ions/cm2 at 300 K. The observed changes in the Modulus spectra depict the disorder induced due to high energy loss of Ag12+ ions in 6H-SiC. The results indicate that the relaxation times were affected by the free charge carriers trapped at the electrically active defect states.