INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER J. Phys.: Condens. Matter 17 (2005) L359–L366 doi:10.1088/0953-8984/17/34/L01 LETTER TO THE EDITOR Anisotropy of ferromagnetism in Co-implanted rutile N Akdogan 1,2 , B Z Rameev 1,3 , L Dorosinsky 4 , H Sozeri 4 , R I Khaibullin 3 , B Akta¸ s 1 , L R Tagirov 3,5,6 , A Westphalen 2 and H Zabel 2 1 Gebze Institute of Technology, 41400 Gebze-Kocaeli, Turkey 2 Institute f¨ ur Experimentalphysik/Festk¨ orperphysik, Ruhr-Universit¨ at Bochum, D-44780 Bochum, Germany 3 Kazan Physical-Technical Institute of RAS, 420029 Kazan, Russia 4 TUBITAK-UME (National Metrology Institute), PK 54, 41470 Gebze-Kocaeli, Turkey 5 Kazan State University, 420008 Kazan, Russia E-mail: Lenar.Tagirov@ksu.ru Received 18 July 2005 Published 12 August 2005 Online at stacks.iop.org/JPhysCM/17/L359 Abstract Magnetic anisotropy of cobalt implanted single-crystalline rutile has been studied by means of magneto-optical Kerr effect (MOKE) and superconducting quantum interference device (SQUID) techniques. We observed for the first time strong angular dependence of the remanent magnetization and coercive field in the plane of the implanted surface: twofold anisotropy for the (100)-substrate and fourfold anisotropy for the (001)-substrate samples. The observation opens up new possibilities to tailor magnetic anisotropies of the material. Possible origins of ferromagnetism and anisotropies in dielectric and diamagnetic single-crystalline TiO 2 samples after Co-ion implantation are discussed. 1. Introduction Rapid progress in electronic devices that incorporate not only charge but also spin of electrons is the subject for a new branch of electronics, so-called spintronics [1–3]. The key problem in development of such devices is efficiency of injection of the spin-polarized current from a ferromagnetic material into a semiconductor. Due to the well known problem of a resistance mismatch at metal/semiconductor interfaces, hindering an effective spin injection [4], much is now concentrated on the development of room-temperature ‘ferromagnetic semiconductors’, such as Mn-doped Ga(In)As, MnGe [2, 3], and Co-doped ZnO [3, 5]. In this respect, recent observations of room-temperature ferromagnetism in Co-doped TiO 2 have attracted considerable attention to titanium dioxide as a host material for magnetic doping [6–11]. 6 Author to whom any correspondence should be addressed. 0953-8984/05/340359+08$30.00 © 2005 IOP Publishing Ltd Printed in the UK L359