  We study the magnetic properties of single crystals of rutile TiO2 implanted
with cobalt for various fluences. The temperature variation of zero field
cooled(ZFC) and field cooled (FC) magnetization shows a much higher blocking
temperature (TB) along [1-10]. Similarly the scaling of magnetization isotherms
above TB is seen only when the field is parallel to [1-10] direction. With
field along this direction, the magnetization shows near saturation at a much
smaller field compared to that of[001] direction. The Co nanoclusters possess
an "easy" and "hard axis" of magnetization coupled by the magneto crystalline
anisotropy of secondary phases of cobalt with TiO2. In addition, at T=2 K we
observe a crossover in the magnetization vs field isotherms between the two
field directions in the samples which has been attributed to the anisotropic
paramagnetism arising from cobalt present in 2+ ionic state with S = 3/2.
