Highly ordered ultralong magnetic nanowires wrapped in stacked graphene layers.
We report on the synthesis and magnetic characterization of ultralong (1 cm) arrays of highly ordered coaxial nanowires with nickel cores and graphene stacking shells (also known as metal-filled carbon nanotubes). Carbon-containing nickel nanowires are first grown on a nanograted surface by magnetron sputtering. Then, a post-annealing treatment favors the metal-catalyzed crystallization of carbon into stacked graphene layers rolled around the nickel cores. The observed uniaxial magnetic anisotropy field oriented along the nanowire axis is an indication that the shape anisotropy dominates the dipolar coupling between the wires. We further show that the thermal treatment induces a decrease in the coercivity of the nanowire arrays. This reflects an enhancement of the quality of the nickel nanowires after annealing attributed to a decrease of the roughness of the nickel surface and to a reduction of the defect density. This new type of graphene-ferromagnetic-metal nanowire appears to be an interesting building block for spintronic applications.
Institut des Matériaux Jean Rouxel, IMN, Université de Nantes, CNRS, 2 rue de la Houssinière, BP 32229, 44322 Nantes cedex 3, France, Telephone: +33 (0) 240 376 434.
Abdel-Aziz
AA
El Mel
Jean-Luc
JL
Duvail
Eric
E
Gautron
Wei
W
Xu
Chang-Hwan
CH
Choi
Benoit
B
Angleraud
Agnès
A
Granier
Pierre-Yves
PY
Tessier
carbon; ferromagnetic; graphene; nanofabrication; nanowires; nickel; phase separation