Surface magnetism and proximity effects in hexaboride thin films

Journal Article · 06 March 2017 · Applied Physics Letters

DOI: https://doi.org/10.1063/1.4978433 · OSTI ID:1466023

Cen, Cheng  ^[1]; Ma, Yanjun ^[2]; Wang, Qiang ^[1]; Eom, Chang -Beom ^[2]

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1. West Virginia Univ., Morgantown, WV (United States)
2. Univ. of Wisconsin, Madison, WI (United States)

Here, the unexpected ferromagnetism in alkaline hexaborides has attracted extensive research efforts. The exceptionally high Curie temperature sustained by very low density of magnetic moments is yet to be clearly understood. Here, we report the magnetic properties studied in CaB₆ and SrB₆ thin films and their heterostructures with SmB₆ grown by pulsed laser deposition. A coexistence of ferromagnetic and superparamagnetic orders with 2D-type magnetic anisotropy was observed in CaB₆ and SrB₆. Boron deficiency and closely correlated local oxidization were found at the film surface that contacts air and its interface with the oxide substrate. These results suggest that the magnetism observed is likely generated by two thin surface/interface layers with high concentration of boron vacancies which are energetically stabled by oxygen cation. Additionally, clear suppression of the superconductivity proximity effect in SmB₆ film was observed when SmB₆ was grown on top of the magnetic CaB₆. Such results demonstrate the interesting perspective of engineering multifunctional heterostructures by coupling the surface magnetic layer with the diversity of other hexaboride materials.

• Research Organization: West Virginia Univ., Morgantown, WV (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: SC0010399
• OSTI ID: 1466023
• Alternate ID(s): OSTI ID: 1349381
• Journal Information: Applied Physics Letters, Vol. 110, Issue 10; ISSN 0003-6951
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English