Computational prediction of a two-dimensional semiconductor SnO2 with negative Poisson's ratio and tunable magnetism by doping

Based on first-principles calculations, we predict a stable two-dimensional semiconductor, namely tin dioxide SnO2. By investigating its dynamical, thermal, and mechanical properties, we find that SnO2 monolayer is an auxetic material with a large in-plane negative Poisson's ratio. Furthermore, our results show that SnO2 is an indirect-gap semiconductor with a band gap in the region of 3.7 eV and an extremely high electron mobility, similar to 10(3) cm(2)V(-1)s(-1). Interestingly, the band structure of SnO2 presents double Mexican-hat-like band edges in the valence bands near the Fermi level. Due to such a unique band feature, a ferromagnetic phase transition takes place with a half-metallic ground state that can be induced by hole doping within a very wide concentration range. Such a magnetic phase can be well explained by the Stoner mechanism. A peculiar feature of the magnetic state is the presence of large magnetocrystalline anisotropy that can switch from in-plane to out-of-plane upon hole doping. Hence, SnO2 monolayer can be tuned to be either an XY magnet or an Ising one, with a magnetic critical temperature above room temperature at proper hole concentrations. These findings demonstrate that the predicted phase of SnO2 is a rare example of p-type magnetism and a possible candidate for spintronic applications.