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Magnetic Rare Earth (Gd) Implanted Tetrahedral Amorphous Carbon (ta-C)

Published online by Cambridge University Press:  01 February 2011

Li Zeng ,
Erik Helgren ,
Hayo Zutz ,
Carsten Ronning  and
Frances Hellman
Li Zeng
Affiliation:
li_zeng@berkeley.edu, University of California, San Diego, Materials Science and Engineering Program, 2306 Roosevelt Ave., Berkeley, CA, 94703, United States, 510-643-4112, 510-643-8497
Erik Helgren
Affiliation:
helgren@berkeley.edu, University of California, Berkeley, Physics Department, 366 Le Conte, Berkeley, CA, 94720, United States
Hayo Zutz
Affiliation:
hzutz@gwdg.de, University of Göttingen, II. Institute of Physics, Friedrich-Hund-PLatz 1, Gottingen, N/A, 37077, Germany
Carsten Ronning
Affiliation:
Carsten.Ronning@phys.uni-goettingen.de, University of Göttingen, II. Institute of Physics, Friedrich-Hund-PLatz 1, Gottingen, N/A, 37077, Germany
Frances Hellman
Affiliation:
fhellman@berkeley.edu, University of California, Berkeley, Physics Department, 366 Le Conte, Berkeley, CA, 94720, United States
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Abstract

Tetrahedrally bonded amorphous carbon (ta-C) thin films were prepared by mass selected ion beam deposition (MSIBD) using 100 eV carbon ions at room temperature. Gadolinium, a magnetic rare earth element, was implanted as a dopant into ta-C with two different fluences. The doping level of the ta-C:Gdx layers was in maximum 4 or 7 at.%, respectively. The Gd is believed to be electrically activated in as-implanted films, although contributions from the sp2 sites cannot be ruled out. A transition temperature (T') was found, below which there is a large negative magnetoresistance (MR) with a strong temperature dependence. Thermal annealing greatly increases the sample conductivity due to the increase of sp2 sites. However, the MR persists at least up to an annealing temperature of 500°C. Magnetically, the Gd dopants behave like non-interacting local moments. Similarities and differences in physical properties between the ta-C:Gdx films and other Gd doped amorphous semiconductors are compared.

Keywords

magnetoresistance (transport)semiconductingC
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 941: Symposium Q – Magnetic Thin Films, Heterostructures, and Device Materials , 2006 , 0941-Q08-22
Copyright
Copyright © Materials Research Society 2006

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