Structure and magnetic properties of Gd nanoparticles and carbon coated Gd/GdC2 nanocapsules
Abstract
Gd nanoparticles and carbon coated Gd/GdC2 nanocapsules have been prepared by means of arc discharge in argon and methane, respectively. In the Gd nanoparticles, gadolinium oxide was detected by x-ray diffraction, while the presence of metallic gadolinium was proved by oxygen analysis and x-ray photoelectron spectra. In the nanocapsules, the existence of GdC2 and Gd was detected by x-ray diffraction. Shell/core structures were observed for either the nanoparticles (with diameters larger than 20 nm) or the nanocapsules. The magnetization data above 25 K, when scaled as a function of μ0H/T, fall on a universal curve while the deviation of the magnetization curves at 4.2 K from the universal curves was ascribed to the superparamagnetism-ferromagnetism transition of small Gd particles. The temperature dependence of magnetization supports the theoretical predictions for very tiny Gd nanoparticles. The presence of metallic Gd in these nanocapsules results in comparatively high magnetization of about 60.5 A m2/kg at 4.2 K, compared with the carbon-coated gadolinium carbide nanocapsules without the metallic Gd core. The possibility of the existence of the spin-glass-like state is discussed for Gd(O) nanoparticles and Gd(C) nanocapsules.
- Publication:
-
Journal of Applied Physics
- Pub Date:
- November 2003
- DOI:
- 10.1063/1.1619192
- Bibcode:
- 2003JAP....94.6779S
- Keywords:
-
- 61.46.+w;
- 75.50.Tt;
- 81.05.Uw;
- 81.05.Bx;
- 75.40.-s;
- 75.50.Cc;
- 75.60.Ej;
- 81.07.Bc;
- 81.07.Wx;
- Fine-particle systems;
- nanocrystalline materials;
- Carbon diamond graphite;
- Metals semimetals and alloys;
- Critical-point effects specific heats short-range order;
- Other ferromagnetic metals and alloys;
- Magnetization curves hysteresis Barkhausen and related effects;
- Nanocrystalline materials;
- Nanopowders