No abstract

The sheet resistance Rs of Ar + irradiated SrTiO3 in patterns with a length scale of several microns increases significantly below ~40 K in connection with driving currents exceeding a certain threshold. The initial lower Rs is recovered upon warming with accelerated recovery around 70 and 160 K. Scanning SQUID microscopy shows local irreversible changes in the spatial distribution of the current with a length scale of several microns. We attribute the observed non-uniform enhancement of Rs to the attraction of the charged single-and di-oxygen vacancies by the crystallographic domain boundaries in SrTiO3. The boundaries which are nearly ferroelectric below 40 K are polarized by the local electrical field associated with the driven current and the clustered vacancies which suppress conductivity in their vicinity yield a noticeable enhancement in the device resistance when the current path width is on the order of the boundary extension. The temperatures of accelerated conductivity recovery are associated with the energy barriers for the diffusion of the two types of vacancies.2

SrRuO3 films have large uniaxial magnetocrystalline anisotropy tilted out of the film plane. When cooled in zero field from above the Curie temperature (∼ 150 K), a magnetic domain structure emerges in the form of 200 nm wide stripes oriented along the in-plane projection of the magnetic easy axis. We measure the interface resistance of the magnetic domain walls by applying a magnetic field perpendicular to the easy axis in the domain wall plane and perpendicular to this plane and observe hysteretic behavior. Micromagnetic simulations of the results indicate that depending on the direction in which the field is applied the domain wall type (Bloch or Néel) and chirality can be tuned.