Strong magnetic coupling in a magnetically dilute f-electron insulator: A dysprosium boron-cluster compound.

Unexpectedly strong magnetic coupling is observed in boride insulators containing the B12 icosahedra as a structural unit. We have successfully synthesized Dy0.74B22C2N, which takes the RB22C2N-type crystal structure. The Dy phase was previously thought to not be possible to form. Spin glass-like behavior was observed with a broad peak in the zero field cooled (ZFC) magnetic susceptibility at T ∼ 44 K, while a large divergence for ZFC and field cooled (FC) curves is observed. The Curie-Weiss constant is determined to be θ=-43.9 K, and this system is indicated to have the strongest magnetic coupling ever observed for any rare earth boride insulator. Electronic structure and chemical bonding calculations were also made. Conventional mechanisms for f-electron magnetism cannot explain the strong coupling observed, which further indicates that the B12 icosahedra is functioning as a novel mediator of magnetic interaction. [ABSTRACT FROM AUTHOR]