Possible metamagnetic origin of ferromagnetism in transition-metal-doped SnO2

Room-temperature ferromagnetism has been observed recently in Co and Fe doped SnO2 powders. In Sn0.99Co0.01O2 powders prepared at 600 °C, ferromagnetism emerged following a sharp transition in the M vs H data at a critical field ∼25kOe. Broad susceptibility maxima were observed in ferromagnetic Sn1−xCoxO2 and Sn1−xFexO2 powders centered near 290 and 260 K, respectively, indicating spin fluctuation effects. High temperature magnetic measurements of Sn0.99Co0.01O2 and Sn0.99Fe0.01O2 obtained TC’s of 440 and 850 K respectively. However, unlike conventional ferromagnets, the magnetic transitions at the TC were associated with sharp changes in M. It is argued that these observed unusual magnetic features indicate a metamagnetic origin of the room-temperature ferromagnetism in Co and Fe doped SnO2.