Magnetic properties of carbon-coated rare-earth carbide nanocrystallites produced by a carbon arc method

• Published in: Journal of applied physics 1994-05, Vol.75 (10), p.5879-5881
• Main Authors: Diggs, B., Zhou, A., Silva, C., Kirkpatrick, S., Nuhfer, N. T., McHenry, M. E., Petasis, D., Majetich, S. A., Brunett, B., Artman, J. O., Staley, S. W.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.355547

Carbon-coated gadolinum and holmium carbide nanocrystallites have been generated using a modification of the Huffman-Krätschmer carbon arc process. Bulk amounts of these particles were isolated from the other by-products using a magnetic field gradient. Transmission electron microscopy revealed the presence of 10–50 nm diameter crystallites coated with numerous graphitic layers. The nanocrystallite phases were identified as Gd2C3 and Ho2C3, respectively, by x-ray and electron diffraction. Magnetization measurements were performed using a superconducting quantum interference device magnetometer between ±5 T at temperatures ranging from 4 to 200 K. The magnetization curves were shown to scale as a function of H/T. The RE3+ sites in RE2C3 have C3 site symmetry. For Gd2C3 the universal curve was fit with a Brillouin function consistent with the Gd3+ free-ion ground-state values of J=7/2 and g=2. The 5I8 Ho3+ free-ion ground state is split, presumably due to a C3 symmetry crystal field. Consequently, for Ho2C3 the Ho3+ free-ion parameters could not be used to fit the experimental data. Empirical fits to the Brillouin function yield a reduced moment of 7.5μB, compared to the free-ion value of 10.6μB. A similarly reduced moment was observed in holmium-containing endohedral fullerenes.