Publications - DO NOT EDIThttp://hdl.handle.net/10106/49742024-03-26T16:35:13Z2024-03-26T16:35:13ZPhase Transformation and Magnetic Hardening in Isolated FePt NanoparticlesLiu, J. PingRong, Chuan-BingNandwana, VikasPoudyal, NarayanChaubey, Girija S.http://hdl.handle.net/10106/50282023-11-21T19:11:21Z2009-07-01T00:00:00ZPhase Transformation and Magnetic Hardening in Isolated FePt Nanoparticles
Liu, J. Ping; Rong, Chuan-Bing; Nandwana, Vikas; Poudyal, Narayan; Chaubey, Girija S.
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 of isolation between FePt
nanoparticles on the phase transition temperature and magnetic
properties has been studied systematically by thermal, magnetic,
and structural characterizations and analyses. It was found that
the A1 to L10 phase transition temperature is dependent sensitively
on the amount of isolation medium. The transition temperature
shift reaches 150–200 ◦C from nonisolated particle assemblies
to completely isolated particles, which may be attributed to the
high activation energy of the phase transformation for the isolated
particles.
Manuscript received December 16, 2008; revised February 24, 2009. First
published March 31, 2009; current version published July 9, 2009.
2009-07-01T00:00:00ZPhase Transformation and Magnetic Hardening in Isolated FePt NanoparticlesLiu, J. PingRong, Chuan-BingNandwana, VikasPoudyal, NarayanChaubey, Girija Shankarhttp://hdl.handle.net/10106/50202023-11-21T19:09:26Z2009-03-31T00:00:00ZPhase Transformation and Magnetic Hardening in Isolated FePt Nanoparticles
Liu, J. Ping; Rong, Chuan-Bing; Nandwana, Vikas; Poudyal, Narayan; Chaubey, Girija Shankar
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. The effect of isolation between FePt nanoparticles on the phase transition temperature and magnetic properties has been studied systematically by thermal, magnetic, and structural characterizations and analyses. It was found that the A1 to L10 phase transition temperature is dependent sensitively on the amount of isolation medium. The transition temperature shift reaches 150-200degC from nonisolated particle assemblies to completely isolated particles, which may be attributed to the high activation energy of the phase transformation for the isolated particles.
2009-03-31T00:00:00ZTransformation of electrical transport from variable range hopping to hard gap resistance in Zn[subscript]1−[subscript]xFe[subscript]xO[subscript]1[subscript]v magnetic semiconductor filmsTian, Y.F.Yan, Shi-ShenZhang, Y.P.Song, H.Q.Ji, G.Liu, G.L.Mei, M.L.Liu, J. PingAltuncevahir, B.Chakka, V.Chen, Y.X.http://hdl.handle.net/10106/50172023-10-18T15:12:15Z2006-11-16T00:00:00ZTransformation of electrical transport from variable range hopping to hard gap resistance in Zn[subscript]1−[subscript]xFe[subscript]xO[subscript]1[subscript]v magnetic semiconductor films
Tian, Y.F.; Yan, Shi-Shen; Zhang, Y.P.; Song, H.Q.; Ji, G.; Liu, G.L.; Mei, M.L.; Liu, J. Ping; Altuncevahir, B.; Chakka, V.; Chen, Y.X.
Transformation of the electrical transport from the Efros and Shklovskii [J. Phys. C 8, L49 (1975)] variable range hopping to the “hard gap” resistance was experimentally observed in a low temperature range as the Fe compositions in Zn1−xFexO1−v ferromagnetic semiconductor films increase. A universal form of the resistance versus temperature, i.e., ρ∝exp[TH/T+(TES/T)1/2], was theoretically established to describe the experimental transport phenomena by taking into account the electron-electron Coulomb interaction, spin-spin exchange interaction, and hard gap energy. The spin polarization ratio, hard gap energy, and ratio of exchange interaction to Coulomb interaction were obtained by fitting the theoretical model to the experimental results. Moreover, the experimental magnetoresistance was also explained by the electrical transport model.
2006-11-16T00:00:00ZObservation of L1[subscript]0-like chemical ordering in a decahedral FePt nanoparticle by C[subscript]s-corrected high resolution transmission electron microscopyHu, XuerangXie, LinZhu, JingPoudyal, NarayanLiu, J. PingYuan, Junhttp://hdl.handle.net/10106/50162023-10-18T15:54:38Z2009-03-09T00:00:00ZObservation 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
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 spherical aberration correction, it is possible to directly correlate the image intensity with the local state of chemical ordering through the help of a multislice image simulation. We have found direct evidence for the image intensity oscillation from one atomic layer to another. It is interpreted as L10-like chemical ordering, i.e., the alternate occupation of Fe and Pt atoms in the (002) planes. The result suggests that chemical ordering survives even in decahedral nanoparticles down to 3 nm size despite the possible surface effects.
PROCEEDINGS OF THE 53RD ANNUAL CONFERENCE ON MAGNETISM AND MAGNETIC MATERIALS / Hard Magnetic Materials
2009-03-09T00:00:00Z