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Kumar, Shalendra,Sharma, S.K.,Alimuddin, S.K.,Knobel, M.,Choudhary, R.J.,Lee, Chan Gyu,Koo, B.H.,Kumar, Ravi Elsevier 2009 Current Applied Physics Vol.9 No.5
<P><B>Abstract</B></P><P>We present here a comparative study on structural and magnetic properties of bulk and thin films of Mg<SUB>0.95</SUB>Mn<SUB>0.05</SUB>Fe<SUB>2</SUB>O<SUB>4</SUB> ferrite deposited on two different substrates using X-ray diffraction (XRD) and dc magnetization measurements. XRD pattern indicates that the bulk sample and their thin films exhibit a polycrystalline single phase cubic spinel structure. It is found that the film deposited on indium tin oxide coated glass (ITO) substrate has smaller grain size than the film deposited on platinum coated silicon (Pt–Si) substrate. Study of magnetization hysteresis loop measurements infer that the bulk sample of Mg<SUB>0.95</SUB>Mn<SUB>0.05</SUB>Fe<SUB>2</SUB>O<SUB>4</SUB> and its thin film deposited on Pt–Si substrate shows a well-defined hysteresis loop at room temperature, which reflects its ferrimagnetic behavior. However, the film deposited on ITO does not show any hysteresis, which reflects its superparamagnetic behavior at room temperature.</P>
INFLUENCE OF Co DOPING ON STRUCTURAL, OPTICAL AND MAGNETIC STUDIES OF Co-DOPED CeO2 NANOPARTICLES
SHALENDRA KUMAR,B. H. KOO,S. K. SHARMA,M. KNOBEL,C. G. LEE 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2010 NANO Vol.5 No.6
We have used the co-precipitation technique to synthesize nanocrystalline Co-doped CeO2 dilute magnetic semiconductors with Co concentrations ranging from 0.0–0.07. X-ray diffraction patterns (XRD) demonstrate that all the samples display single phase cubic structure without any impurity phase. Average particle sizes calculated from XRD and transmission electron microscopy (TEM) studies showed a gradual decrease with increase in Co ions concentration. UV–visible optical spectroscopy measurements reflect an energy band gap, which decreases with the increasing concentration of dopant (x ≤ 0.03). Raman spectra show an intensity loss of classical CeO2 vibration modes, which is an indication of considerable structural modifications and disorder in CeO2 lattice. Magnetic measurements revealed that all the samples exhibit a weak ferromagnetism at room temperature.
Structural and magnetic properties of chemically synthesized Fe doped ZnO
Kumar, Shalendra,Kim, Y. J.,Koo, B. H.,Sharma, S. K.,Vargas, J. M.,Knobel, M.,Gautam, S.,Chae, K. H.,Kim, D. K.,Kim, Y. K.,Lee, C. G. American Institute of Physics 2009 JOURNAL OF APPLIED PHYSICS - Vol.105 No.7
<P>We report on the synthesis of Fe-doped ZnO with nominal composition of Zn0.99Fe0.01O by using a coprecipitation method. X-ray diffraction and selective area electron diffraction studies reveal a single phase wurtzite crystal structure without any secondary phase. Field emission transmission electron microscopy measurements infer that Zn0.99Fe0.01O have nanorod-type microstructures. Magnetic hysteresis measurement performed at different temperatures show that Zn0.99Fe0.01O exhibits a weak ferromagnetic behavior at room temperature. A detailed investigation of the electronic and local structure using O K-, Fe L-3,L-2 near edge x-ray absorption fine structure suggests that Fe is substituting Zn in ZnO matrix and is in Fe3+ state. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3073933]</P>
Effect of hydrazine on structural, morphological and magnetic properties of SmCo-Co nanocomposites
Kumari Kavita,Kumar Akshay,Park Su-Jeong,Sharma Mohit K.,Yadav Naveen,Kumar Manish,Kumar Shalendra,Huh Seok-Hwan,Kim Jong-Woo,Koo Bon-Heun 한국물리학회 2023 Current Applied Physics Vol.53 No.-
In the present work, one-dimensional (1-D) SmCo-Co magnetic nanocomposites are prepared in a single-pot chemical synthesis in the presence of external magnetic field with varying amounts of hydrazine hydrate with samples named as: SC-2 mL, SC-4 mL, SC-6 mL and SC-8 mL. The Rietveld refinement of XRD patterns revealed the formation of Sm2Co17 (P63/mmc), Sm(OH)3 (P63/m) and hcp-Co (P63/mmc) phases. The 1-D nanocomposites are found to possess the highest aspect ratio (~6.3), lowest crystallite size (~49 nm) and highest developed strain (~4.76 x 10-3) corresponding to SC-4 mL. The magnetic response of the samples is found to be affected by the hydrazine amount showing highest saturation magnetization (~156 emu/g) and effective magnetic anisotropy (~1.2 x 106 erg/cm3) for SC-4 mL with highest exchange coupling observed using Bloch law fitting. The results indicate suppressing behaviour of hydrazine amount to be utilized up to a certain limit.