Coverage and strain dependent magnetization of titanium-coated carbon nanotubes

First-principles, spin-relaxed pseudopotential plane wave calculations show that $\mathrm{Ti}$ atoms can form a continuous coating of carbon nanotubes at different amounts of coverage. Fully relaxed geometry has a complex but regular atomic structure. The semiconducting tube becomes ferromagnetic metal with high quantum conductance. However, the magnetic properties of $\mathrm{Ti}\text{\ensuremath{-}}$ coated tubes depend strongly on the geometry, amount of $\mathrm{Ti}$ coverage and also on the elastic deformation of the tube. While the magnetic moment can be pronounced significantly by the positive axial strain, it can decrease dramatically upon the adsorption of additional $\mathrm{Ti}$ atoms to those already covering the nanotube. Besides, the electronic structure and the spin-polarization near the Fermi level can also be modified by radial strain.