Ferromagnetism on a paramagnetic host background: the case of rutile TM:TiO2 single crystals (TM=Cr,Mn,Fe,Co,Ni,Cu)

Single crystals of TiO2 rutile doped with Cr, Mn, Fe, Co, Ni, and Cu were grown with the flux method in a Na2B4O7 melt. The samples, checked in their structural and phase homogeneity by x-ray diffraction and micro-Raman spectroscopy, were single-phase needle-shaped crystals several millimetres long. Paramagnetic and ferromagnetic behaviours at room temperature were observed and they are discussed also in connection with the magnetic properties of undoped TiO2 crystals.