Persistent Optically Induced Magnetism in Oxygen-Deficient Strontium   Titanate
  Strontium titanate (SrTiO$_3$) is a foundational material in the emerging field of complex oxide electronics. While its electronic and optical properties have been studied for decades, SrTiO$_3$ has recently become a renewed materials research focus catalyzed in part by the discovery of magnetism and superconductivity at interfaces between SrTiO$_3$ and other oxides. The formation and distribution of oxygen vacancies may play an essential but as-yet-incompletely understood role in these effects. Moreover, recent signatures of magnetization in gated SrTiO$_3$ have further galvanized interest in the emergent properties of this nominally nonmagnetic material. Here we observe an optically induced and persistent magnetization in oxygen-deficient SrTiO$_{3-\delta}$ using magnetic circular dichroism (MCD) spectroscopy and SQUID magnetometry. This zero-field magnetization appears below ~18K, persists for hours below 10K, and is tunable via the polarization and wavelength of sub-bandgap (400-500nm) light. These effects occur only in oxygen-deficient samples, revealing the detailed interplay between magnetism, lattice defects, and light in an archetypal oxide material. 
W. D. Rice, P. Ambwani, M. Bombeck, J. D. Thompson, C. Leighton, S. A.   Crooker
cond-mat.mes-hall cond-mat.mtrl-sci