Origin of the Magnetism in Undoped and Mn-Doped SnO₂ Thin Films: Sn vs Oxygen Vacancies

Abstract

SnO 2 and Mn-doped SnO 2 thin films have been grown by radio frequency sputtering in two different atmospheres (Ar and Ar/O 2 ) on Si(100) and Al 2 O 3 (R-cut) at room temperature (RT) and at 500 °C. The RT films are amorphous; those grown at 500 °C are polycrystalline or epitaxial, depending on the substrate. All the films, undoped or Mn-doped, present a paramagnetic signal, and ferromagnetism is not observed, regardless of the growth conditions or their structure. The measured magnetization systematically decreases when the films are grown in oxygen-free atmosphere, thus indicating that magnetism is not promoted by oxygen vacancies, and no correlation is found between conductivity and magnetism. We compare the experimental results with ab initio density functional calculations and demonstrate that the Sn vacancies are the origin of the measured magnetization in SnO 2 undoped films. Oxygen vacancies contribute to neither the magnetic moment nor the conductivity of the samples. The localized nature of the defect-induced electronic levels prevents a collective magnetic or conducting behavior.

Magnetism of Zn-doped SnO2: Role of surfaces

“…In agreement with previous theory 26,40,41 and experiments, 44 neutral and doubly ionized oxygen vacancies are found to be nonmagnetic in bulk SnO 2 . However, singly ionized oxygen vacancy is found to be magnetic with a total magnetization of 0.35 l B .…”

Defect driven ferromagnetism in SnO2: a combined study using density functional theory and positron annihilation spectroscopy

“…SnO 2 is a wide band gap (~ 3.6 eV at room temperature) n-type semiconductor. In recent times, the occurrence of room temperature ferromagnetic ordering in undoped SnO 2 has been reported [14][15][16][17] saturation magnetization (M s ). In SnO 2 nanowires, strong and tunable ferromagnetic response by ultraviolet light irradiation has been observed.…”

Lithium doping effects on structural and ferromagnetic properties of Sn0.95Ni0.05O2

“…Since Dietl et al [2] theoretically predicted the room-temperature ferromagnetism of nonmagnetic oxide and nitride semiconductors by doping magnetic transition-metal (TM) elements, much attention has been cast on ZnO-based [3][4][5][6][7], TiO 2 -based [8,9] and SnO 2 -based [10][11][12][13] DMSs. And defects are believed to explain why there exists a long-ranged ferromagnetism [14,15] that is often called "d 0 ferromagnetism" [16].…”