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

Publisher Website
Google Scholar
Abstract
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.

This publication has 8 references indexed in Scilit: