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Synthesis and surface modified hard magnetic properties in Co0.5Pt0.5 nanocrystallites from a rheological liquid precursor
- Source :
-
Journal of Magnetism & Magnetic Materials . Nov2012, Vol. 324 Issue 22, p3893-3898. 6p. - Publication Year :
- 2012
-
Abstract
- Abstract: Small crystallites of a metastable phase Co0.5Pt0.5 are precipitated by heating a rheological liquid precursor of cobalt–hydrazine complex and platinum chloride H2PtCl6·xH2O in polymer molecules of poly(vinylpyrrolidone) (PVP) in ethylene glycol. The hydrazine co-reduces nascent atoms from the Co2+ and Pt4+ that recombine and grow as Co0.5Pt0.5. The PVP molecules cap a growing Co0.5Pt0.5 as it achieves a critical size so that it stops growing further in given conditions. X-ray diffraction pattern of a recovered powder reveals a crystalline Co0.5Pt0.5 phase (average crystallite size D∼8nm) of a well-known Fm3m-fcc crystal structure with the lattice parameter a=0.3916nm (density ρ=14.09g/cm3). A more ordered L10 phase (ρ=15.91g/cm3) transforms (D≥25nm) upon annealing the powder at temperature lesser than 700°C (in vacuum). At room temperature, the virgin crystallites bear only a small saturation magnetization M s=5.54emu/g (D=8nm) of a soft magnet and it hardly grows on bigger sizes (D≤31nm) in a canted ferromagnetic structure. A rectangular hysteresis loop is markedly expanded on an optimally annealed L10 phase at 800°C for 60min, showing a surface modified coercivity H c=7.781kOe with remnant ratio M r/M s=0.5564, and M s=39.75emu/g. Crystallites self-assembled in an acicular shape tailor large H c from ideal single domains and high magnetocrystalline anisotropy of a hard magnet L10 phase. [Copyright &y& Elsevier]
Details
- Language :
- English
- ISSN :
- 03048853
- Volume :
- 324
- Issue :
- 22
- Database :
- Academic Search Index
- Journal :
- Journal of Magnetism & Magnetic Materials
- Publication Type :
- Academic Journal
- Accession number :
- 78282153
- Full Text :
- https://doi.org/10.1016/j.jmmm.2012.06.041