Semicon ducting high-temperature magnets?

In recent years, calcium hexaboride (CaB₆) doped with lanthanum has puzzled magnetism researchers, in large part because it retains a modest ferromagnetism even at 900 K—a surprisingly high Curie temperature for a compound that does not contain traditional magnetic metals such as nickel or iron. Electronic structure calculations based on density functional theory led to several possible explanations: CaB₆ might be a semimetal or an excitonic insulator; doped CaB₆ might be a doped excitonic insulator, a conventional magnetic material, or even an example of the long-sought, low-density spin-polarized electron gas. Now, however, physicists in the Netherlands have performed more accurate calculations, using the so-called GW approximation, which suggest that CaB₆ is actually a semiconductor with a bandgap of 0.8 eV. If that is true, important applications await the compound in the field of spintronics, in which an electron’s spin and not just its charge carries information. Thus far, combining semiconductors with magnetic metals has been difficult, especially at or above room temperature. In addition, new magnetic sensor and memory applications might be possible. (H. J. Tromp et al.., Phys. Rev. Lett. 87 , 016401, 2001 http://dx.doi.org/10.1103/PhysRevLett.87.016401 )