Browsing Department of Physics by Author "Poudyal, Narayan"
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Bulk FePt-based nanocomposite magnets with enhanced exchange coupling
Rong, Chuan-Bing; Nandwana, Vikas; Poudyal, Narayan; Liu, J. Ping; Kozlov, Mikhail E.; Baughman, Ray H.; Ding, Yong; Wang, Zhong Lin (American Institute of PhysicsDepartment of Physics, The University of Texas at Arlington, 2007-07-23)High density bulk FePt/Fe3Pt nanocomposite magnets have been prepared by high-pressure warm compaction of chemically synthesized FePt and Fe3O4 nanoparticles. It is found that the density increases with the compaction ... -
Bulk FePt-based nanocomposite magnets with enhanced exchange coupling
Nandwana, Vikas; Liu, J. Ping; Poudyal, Narayan; Rong, Chuan-Bing; Kozlov, Mikhail E.; Baughman, Ray H.; Ding, Yong; Wang, Zhong Lin (AIP, 2007)High density bulk FePt/Fe3Pt nanocomposite magnets have been prepared by high-pressure warm compaction of chemically synthesized FePt and Fe3O4 nanoparticles. It is found that the density increases with the compaction ... -
Bulk FePt/Fe3Pt nanocomposite magnets prepared by spark plasma sintering
Rong, Chuan-Bing; Nandwana, Vikas; Poudyal, Narayan; Liu, J. Ping; Saito, Tetsuji; Wu, Yaqiao; Kramer, Matthew J. (American Institute of PhysicsDepartment of Physics, The University of Texas at Arlington, 2007-04-27)FePt/Fe3Pt bulk nanocomposite magnets have been prepared by the spark plasma sintering of chemically synthesized FePt and Fe3O4 nanoparticles under 100 MPa at 400–600 °C. It was found that the phase transition of the FePt ... -
Bulk FePt/Fe3Pt nanocomposite magnets prepared by spark plasma sintering
Nandwana, Vikas; Rong, Chuan-Bing; Poudyal, Narayan; Liu, J. Ping; Saito, Tetsuji; Wu, Yaqiao; Kramer, Matthew J. (AIP, 2007)FePt/Fe3Pt bulk nanocomposite magnets have been prepared by the spark plasma sintering of chemically synthesized FePt and Fe3O4 nanoparticles under 100 MPa at 400–600 °C. It was found that the phase transition of the FePt ... -
Effects of particle size and composition on coercivity of Sm–Co nanoparticles prepared by surfactant-assisted ball milling
Poudyal, Narayan; Rong, Chuan-Bing; Liu, J. Ping (American Institute of PhysicsDepartment of Physics, The University of Texas at Arlington, 2010-04-15)The correlation between the recoil loop openness and the activation volume has been studied for the SmCo5/α-Fe nanocomposite powder material prepared by mechanical alloying. The α-Fe phase content in the nanocomposite ... -
Fabrication of bulk nanocomposite magnets via severe plastic deformation and warm compaction,
Rong, Chuan-Bing; Zhang, Ying; Poudyal, Narayan; Xiong, Xiangyuan; Kramer, Matthew J.; Liu, J. Ping (American Institute of PhysicsDepartment of Physics, The University of Texas at Arlington, 2010-03-10)We demonstrate that a SmCo/FeCo based hard/soft nanocomposite material can be fabricated by distributing the soft magnetic α-Fe phase particles homogeneously in a hard magnetic SmCo phase through severe plastic deformation. ... -
Fabrication Of Superparamagnetic And Ferromagnetic Nanoparticles
Poudyal, Narayan (Physics, 2009-09-16)Monodisperse magnetic nanoparticles with controlled size and geometry have drawn great attention in the last decade for fundamental scientific studies and for their potential applications in advanced materials and devices ... -
Hard magnetic FePt nanoparticles by salt-matrix annealing
Nandwana, Vikas; Li, Daren; Poudyal, Narayan; Jin, Zhiqiang; Elkins, Kevin Eugene; Liu, J. Ping (AIP, 2006)To transfer face-centered-cubic (fcc) FePt nanoparticles to the face-centered-tetragonal (fct) phase with high magnetic anisotropy, heat treatments are necessary. The heat treatments lead to agglomeration and sintering of ... -
High thermal stability of carbon-coated L10-FePt nanoparticles prepared by salt-matrix annealing
Nandwana, Vikas; Rong, Chuan-Bing; Poudyal, Narayan; Chaubey, Girija S.; Liu, Yuzi; Wu, Y.Q.; Kramer, M.J.; Kozlov, M.E.; Baughman, Ray H.; Liu, J. Ping (AIP, 2008)Monodisperse L10-FePt nanoparticles with size ranging from 3 to 8 nm were prepared by the salt-matrix annealing method. It was observed that the annealed particles have high thermal stability—no sintering occurred even ... -
High thermal stability of carbon-coated L1[subscript]0-FePt nanoparticles prepared by salt-matrix annealing
Rong, Chuan-Bing; Poudyal, Narayan; Chuabey, Girija S.; Nandwana, Vikas; Liu, Yuzi; Wu, Y.Q.; Kramer, Matthew J.; Kozlov, Mikhail E.; Baughman, Ray H.; Liu, J. Ping (Institute of Applied PhysicsDepartment of Physics, The University of Texas at Arlington, 2008-02-08)Monodisperse L10-FePt nanoparticles with size ranging from 3 to 8 nm were prepared by the salt-matrix annealing method. It was observed that the annealed particles have high thermal stability—no sintering occurred even ... -
Microstructures and magnetic alignment of L10 FePt nanoparticles
Nandwana, Vikas; Kang, Shishou; Shi, Shifan; Jia, Zhiyong; Thompson, G. R.; Nikles, David E.; Harrell, J. W.; Poudyal, Narayan; Liu, J. Ping (AIP, 2009)Chemically ordered FePt nanoparticles were obtained by high temperature annealing a mixture of FePt particles with NaCl. After the NaCl was removed with de-ionized water, the transformed FePt nanoparticles were redispersed ... -
Observation of L1[subscript]0-like chemical ordering in a decahedral FePt nanoparticle by C[subscript]s-corrected high resolution transmission electron microscopy
Hu, Xuerang; Xie, Lin; Zhu, Jing; Poudyal, Narayan; Liu, J. Ping; Yuan, Jun (American Institute of PhysicsDepartment of Physics, The University of Texas at Arlington, 2009-03-09)The state of the chemical ordering in a decahedral FePt nanoparticle was studied using aberration corrected high resolution transmission electron microscopy. With the reduced image delocalization effect as a result of ... -
Phase Transformation and Magnetic Hardening in Isolated FePt Nanoparticles
Liu, J. Ping; Rong, Chuan-Bing; Nandwana, Vikas; Poudyal, Narayan; Chaubey, Girija Shankar (IEEEDepartment of Physics, The University of Texas at Arlington, 2009-03-31)Isolated monodisperse L1[subscript]0 FePt nanoparticles coated by carbon were obtained by adding enough surfactants that decomposed into carbon after the chemical synthesis and postannealing of the A1 FePt nanoparticles. ... -
Phase Transformation and Magnetic Hardening in Isolated FePt Nanoparticles
Liu, J. Ping; Rong, Chuan-Bing; Nandwana, Vikas; Poudyal, Narayan; Chaubey, Girija S. (IEEE XploreIEEEDepartment of Physics, The University of Texas at Arlington, 2009-07)Isolated monodisperseL10 FePt nanoparticles coated by carbon were obtained by adding enough surfactants that decomposed into carbon after the chemical synthesis and postannealing of the A1 FePt nanoparticles. The effect ... -
Rapid thermal annealing of FePt nanoparticles
Yano, Kazuaki; Nandwana, Vikas; Poudyal, Narayan; Rong, Chuan-Bing; Liu, J. Ping (American Institute of PhysicsDepartment of Physics, The University of Texas at Arlington, 2008-07-11)We report a systematic study on rapid thermal annealing (RTA) of FePt nanoparticles. FePt particles with an average size of 8 nm were synthesized by a chemical solution method, and then annealed using RTA and conventional ... -
Rapid thermal annealing of FePt nanoparticles
Nandwana, Vikas; Yano, Kazuaki; Poudyal, Narayan; Rong, Chuan-Bing; Liu, J. Ping (AIP, 2008-07-01)We report a systematic study on rapid thermal annealing (RTA) of FePt nanoparticles. FePt particles with an average size of 8 nm were synthesized by a chemical solution method, and then annealed using RTA and conventional ... -
Shape control of FePt nanocrystals
Poudyal, Narayan; Chaubey, Girija Shankar; Rong, Chuan-Bing; Liu, J. Ping (American Institute of PhysicsDepartment of Physics, The University of Texas at Arlington, 2009-04-06): FePt nanocrystals were prepared by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in properly chosen solvents/surfactants. A variety of FePt nanocrystals, including ... -
Structural phase transition and ferromagnetism in monodisperse 3 nm FePt particles
Rong, Chuan-Bing; Poudyal, Narayan; Chaubey, Girija Shankar; Nandwana, Vikas; Skomski, R.; Wu, Y.Q.; Kramer, Matthew J.; Liu, J. Ping (American Institute of PhysicsDepartment of Physics, The University of Texas at Arlington, 2007-08-30)FePt nanoparticles with a size of 3 nm and thermally stable room-temperature ferromagnetism are investigated. The monodisperse nanoparticles were prepared by chemical synthesis and a salt-matrix annealing technique. ... -
Synthesis And Characterization Of Magnetic Nanoparticles
Poudyal, Narayan (Physics, 2007-08-23)Synthesis of uniform nanoparticles (<100 nm) of hard and soft magnetic materials have attracted much attention in the last two decades because of their unique magnetic properties and potential for many applications such ...