No abstract

No abstract

We present a consistent overall picture of the electronic structure and ferromagnetic interaction in CaB 6 , based on our joint transport, optical, and tunneling measurements on high-quality defect-controlled single crystals. Pure CaB 6 single crystals, synthesized with 99.9999% pure boron, exhibited fully semiconducting characteristics, such as monotonic resistance for 2-300 K, a tunneling conductance gap, and an optical absorption threshold at 1.0 eV. Boron-related defects formed in CaB 6 single crystals synthesized with 99.9% pure boron induced midgap states 0.18 eV below the conduction band and extra free charge carriers, with the transport, optical, and tunneling properties substantially modified. Remarkably, no ferromagnetic signals were detected from single crystals made with 99.9999% pure boron, regardless of stoichiometry, whereas those made with 99.9% boron exhibited ferromagnetism within a finite range of carrier density. The possible surmise between the electronic state and magnetization will be discussed.

No abstract

We have measured room-temperature magneto-optical properties of AuMnSn on a single-crystalline sample. The maximum polar Kerr rotation was predicted to be very large, about −0.7° at 1.2eV [L. Offernes, P. Ravindran, and A. Kjekshus, Appl. Phys. Lett. 82, 2862 (2003)]. We found the experimental maximum Kerr rotation and ellipticity were about three times smaller than predicted and appeared at energies about 0.6eV higher than predicted, which is possibly due to inaccurate handling of the theory based on the local spin-density approximation to density-function theory for the localized 4d and 5d orbitals in AuMnSn.