Study of the oxygen vacancy influence on magnetic properties of Fe- and Co-doped SnO(2) diluted alloys

Transition-metal (TM)-doped diluted magnetic oxides (DMOs) have attracted attention from both experimental and theoretical points of view due to their potential use in spintronics towards new nanostructured devices and new technologies. In the present work, we study the magnetic properties of Sn(0.96)TM(0.04)O(2) and Sn(0.96)TM(0.04)O(1.98)(V(O))(0.02), where TM = Fe and Co, focusing in particular in the role played by the presence of O vacancies nearby the TM. The calculated total energy as a function of the total magnetic moment per cell shows a magnetic metastability, corresponding to a ground state, respectively, with 2 and 1 μ(B)/cell, for Fe and Co. Two metastable states, with 0 and 4 μ(B)/cell were found for Fe, and a single value, 3 μ(B)/cell, for Co. The spin-crossover energies (E(S)) were calculated. The values are E(S)(0/2) = 107 meV and E(S)(4/2) = 25 meV for Fe. For Co, E(S)(3/1) = 36 meV. By creating O vacancies close to the TM site, we show that the metastablity and E(S) change. For iron, a new state appears, and the state with zero magnetic moment disappears. The ground state is 4 μ(B)/cell instead of 2 μ(B)/cell, and the energy E(S)(2/4) is 30 meV. For cobalt, the ground state is then found with 3 μ(B)/cell and the metastable state with 1 μ(B)/cell. The spin-crossover energy E(S)(1/3) is 21 meV. Our results suggest that these materials may be used in devices for spintronic applications that require different magnetization states.