Torque magnetometry of an amorphous-alumina/strontium-titanate interface

We report torque magnetometry measurements of an oxide heterostructure consisting of an amorphous Al$_2$O$_3$ thin film grown on a crystalline SrTiO$_3$ substrate ($a$-AO/STO) by atomic layer deposition. We find a torque response that resembles previous studies of crystalline LaAlO$_3$/SrTiO$_3$ (LAO/STO) heterointerfaces, consistent with strongly anisotropic magnetic ordering in the plane of the interface. Unlike crystalline LAO, amorphous Al$_2$O$_3$ is nonpolar, indicating that planar magnetism at an oxide interface is possible without the strong internal electric fields generated within the polarization catastrophe model. We discuss our results in the context of current theoretical efforts to explain magnetism in crystalline LAO/STO.

[1]  A. Zunger,et al.  A polarity-induced defect mechanism for conductivity and magnetism at polar–nonpolar oxide interfaces , 2014, Nature Communications.

[2]  R. Gordon,et al.  Origin of the self-limited electron densities at Al₂O₃/SrTiO₃ heterostructures grown by atomic layer deposition - oxygen diffusion model. , 2013, Nanoscale.

[3]  H. Hwang,et al.  Titanium dxy ferromagnetism at the LaAlO3/SrTiO3 interface. , 2013, Nature materials.

[4]  M. Randeria,et al.  Ferromagnetic exchange, spin–orbit coupling and spiral magnetism at the LaAlO3/SrTiO3 interface , 2013, Nature Physics.

[5]  R. Gordon,et al.  Creation and control of two-dimensional electron gas using Al-based amorphous oxides/SrTiO₃ heterostructures grown by atomic layer deposition. , 2012, Nano letters.

[6]  H. Hwang,et al.  Direct imaging of the coexistence of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface , 2011, 1108.3150.

[7]  J. Mannhart,et al.  Coexistence of magnetic order and two-dimensional superconductivity at LaAlO3/SrTiO3 interfaces , 2011, 1105.0235.

[8]  T. Venkatesan,et al.  Electronic phase separation at the LaAlO₃/SrTiO₃ interface. , 2011, Nature communications.

[9]  J. Mannhart,et al.  Oxide Interfaces—An Opportunity for Electronics , 2010, Science.

[10]  A. Millis,et al.  Two-Dimensional Electron Gases at Oxide Interfaces , 2008 .

[11]  D. Blank,et al.  Structure–Property Relation of SrTiO3/LaAlO3 Interfaces , 2008, 0809.1068.

[12]  W. G. van der Wiel,et al.  Magnetic effects at the interface between non-magnetic oxides. , 2007, Nature materials.

[13]  D. Muller,et al.  Why some interfaces cannot be sharp , 2005, cond-mat/0510491.

[14]  Akira Ohtomo,et al.  A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface , 2004, Nature.