Observation of true ferromagnetism above room temperature in a diluted magnetic semiconductor.

Since 2000, the intensive effort in materials research to develop a diluted magnetic semiconductor (DMS) exhibiting high-temperature ferromagnetism (HT-FM) above room temperature was not successful. Here, we present the first semiconducting bulk HT-FM DMS, based on LaTa1-xCox(O,N)3-d. The Curie temperature of the materials 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-FM can be excluded, since all applied characterization methods verify phase purity. As anionic vacancies were found, we suggest these as an origin for a complex interaction between defect-like magnetism and the introduced magnetic cobalt ions. This study lays the foundation for the experimental investigation and design of further HT-FM DMS.