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Living dead layer at the surface of a Mott insulator

Rare-earth titanates are Mott insulators, and emerge as promising building blocks to realize exotic electronic states at oxide interfaces. For small rare-earths such as Dy, these titanates are canted ferrimagnets. However, critical to this magnetic order is the 3+ valence of the Ti cations, which is hard to stabilize. In our recent paper just published in Advanced Materials, we report for the first time the growth of high-quality DyTiO3 thin films, with excellent, bulk-like magnetic properties at high thickness, and a surprisingly enhanced saturation magnetization at low thickness. This thickness dependence of the magnetic properties is reminiscent of dead-layer effects in more conventional materials in which magnetization is reduced at low thickness. Through a combination of X-ray spectroscopies and magnetometry we have shown that this “living-dead” magnetic layer arise from uncoupled, paramagnetic Dy ions with neighbouring non-magnetic Ti4+ present at the film surface.

This work was performed in collaboration with the Helmholtz-Zentrum Berlin, the University of Würzburg and the Paul-Scherrer Institute and received financial support from the ERC CoG “MINT” (#6115759) and the region Ile-de-France DIM Oxymore “NEIMO” project.

A Living-Dead Magnetic Layer at the Surface of Ferrimagnetic DyTiO3 Thin Films
R. Aeschlimann et al ; Adv. Mater. 10.1002/adma.201707489