  Since 2000, the intensive effort in materials research to develop a diluted
magnetic semiconductor exhibiting high-temperature (HT) ferromagnetism above
room temperature was not successful. Here, the possible first bulk diluted
HT-ferromagnetic non-metallic materials, based on the perovskite-type
oxynitrides LaTa1-xCox(O,N)3-d (x = 0.01, 0.03, 0.05) are realized. The Curie
temperature of the synthesized powders exceeds 600 K and the sample
magnetizations are large enough to be directly attracted by permanent magnets.
Cobalt clusters as a possible source for the observed HT-ferromagnetism can be
excluded, since all applied characterization methods verify phase purity.
Applied conventional and element-specific magnetometry imply ferromagnetic
intermediate spin (IS) Co3+ which is included in a ferromagnetic host matrix.
This indicates a complex magnetic interplay between the existing crystal
structure, the observed anionic vacancies, and the introduced cobalt ions.
These results lay the foundation for the experimental investigation and design
of further diluted HT-ferromagnetic semiconductors.
