The 215th Special MMU seminar   


Surface magnetism of strontium titanate

Professor J. M. D. Coey
School of Physics, Trinity College,
Dublin, Ireland


Date & Time: 16:00 - 17:00, February 26th (Fri), 2016.
Place: 8F Medium Seminar Room(#811-812), Sengen

Abstract:

  SrTiO3 plays a central role in oxide electronics. It is a substrate of choice for functional oxide heterostructures based on perovskite-structure thin-film stacks, and its surface or interface with a polar oxide such as LaAlO3 can become a two-dimensional conductor owing to electronic reconstruction or the presence of oxygen defects. Various, apparently inconsistent reports of magnetic order in SrTiO3 abound in the literature. Here we undertake a systematic experimental study aimed at establishing how and when SrTiO3 can develop a magnetic moment at room temperature. Besides the intrinsic diamagnetism of SrTiO3, magnetic signals were of three types – a Curie law susceptibility due to dilute magnetic impurities at the sub-ppm level, a hysteretic, temperature-dependent ferromagnetic impurity contribution, and a practically anhysteretic, defect-related temperature-independent component that saturates in about 200 mT. The third component, which can be as large as to 4 Bohr magnetons per nm2 of surface area, is the greatest.