Eur. Phys. J. B 55, 253-260 (2007)
https://doi.org/10.1140/epjb/e2007-00054-2

Anisotropic ferromagnetism induced in rutile single crystals by Co implantation

¹ CFMC-Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal
² LFI, Dep. de Física, ITN, E.N.10, 2686-953 Sacavém, Portugal
³ CFNUL, Av.Prof.Gama Pinto 2, 1649-003 Lisboa, Portugal
⁴ Dep. de Física, Faculdade de Cincias, Universidade de Lisboa, Campo Grande, Ed. C8, 1749-016 Lisboa, Portugal
⁵ Instituto Superior de Engenharia de Lisboa, R. Cons. Emídio Navarro 1, 1950-062 Lisboa, Portugal

Corresponding author: ^a mmcruz@fc.ul.pt

Received: 19 July 2006
Revised: 16 January 2007
Published online: 21 February 2007

Abstract

The magnetic and electrical properties of Co-implanted single crystalline TiO₂ rutile are presented. For fluences of the order of 10¹⁷ cm^-2 and implantation energy of 150 keV the maximum atomic concentration of cobalt is 13 at% at a depth of 65 nm from the surface. The as implanted single crystals exhibit superparamagnetic behaviour attributed to the formation of nanosized cobalt clusters. After annealing at 1073 K an anisotropic ferromagnetic behaviour emerges with the easy magnetization axis lying in the (001) plane of rutile. The ferromagnetic behaviour is associated with oriented cobalt aggregates. Electrical conductivity of the implanted samples annealed in vacuum also exhibits anisotropic behaviour at low temperatures, but no magnetoresistive effects were detected.