Structure-Magnetic Property Relationship in Transition Metal (M=V, Cr, Mn, Fe, Co, Ni) Doped SnO₂ Nanoparticles

This work reports the results of an extensive search for ferromagnetism in SnO₂ doped with a wide range of transition metal cations (M = V, Cr, Mn, Fe, Co, and Ni). By varying the dopant concentration in the 0–12% range, signatures of ferromagnetic behavior in varying degrees were observed with most dopants. The room temperature magnetic moments per dopant ion were low in all the systems and Co (0.13μ_B/ion), Fe (0.014μ_B/ion), and Cr (0.06μ_B/ion) showed relatively the strongest ferromagnetic behavior. In these systems, the observed ferromagnetism initially increased reaching a maximum in the 1–12% range and then gradually weakened and eventually disappeared at higher concentration. The limiting dopant concentration x_L at which ferromagnetic behavior reaches a maximum varies with dopant type and has a strong relation to structural changes revealed from detailed x-ray diffraction (XRD) analysis. The XRD data indicated that the lattice volume for every Sn_1−xM_xO₂ system decreased with increasing x in the 0 ⩽ x_L range. However, for x>x_L, the lattice volume increased dramatically indicating a significant interstitial doping which destroys the ferromagnetic behavior.