2007/01/26 by Li Zeng, L. Zeng, E. Helgren +7
Earth and Planetary Sciences · Materials Science · Physics and Astronomy · #Diamond and Carbon-based Materials Research #Glass properties and applications #High-pressure geophysics and materials #cond-mat.mtrl-sci #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.75.235450
9 figures
arxiv created 2007/01/26 · openalex publication_date 2007/06/29 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The magnetic rare earth element gadolinium (Gd) was doped into thin films of amorphous carbon (hydrogenated a\text\ensuremath-C:H, or hydrogen-free a\text\ensuremath-C) using magnetron cosputtering. The Gd acted as a magnetic as well as an electrical dopant, resulting in an enormous negative magnetoresistance below a temperature (T^\ensuremath'). Hydrogen was introduced to control the amorphous carbon bonding structure. High-resolution electron microscopy, ion-beam analysis, and Raman spectroscopy were used to characterize the influence of Gd doping on the a\text\ensuremath-GdxC_1\ensuremath-x(:Hy) film morphology, composition, density, and bonding. The films were largely amorphous and homogeneous up to x=22.0\phantom\rule0.3em0exat.\phantom\rule0.2em0ex%. As the Gd doping increased, the sp2-bonded carbon atoms evolved from carbon chains to 6-member graphitic rings. Incorporation of H opened up the graphitic rings and stabilized a sp2-rich carbon-chain random network. The transport properties not only depended on Gd doping, but were also very sensitive to the sp2 ordering. Magnetic properties, such as the spin-glass freezing temperature and susceptibility, scaled with the Gd concentration.