High TC ferromagnetism in diluted magnetic semiconducting GaN:Mn films

Wurtzite GaN:Mn films on sapphire substrates were successfully grown by use of the molecular beam epitaxy (MBE) system. The film has an extremely high Curie temperature of around 940 K, although the Mn concentration is only about 3 ~ 5 %. Magnetization measurements were carried out in magnetic fields parallel to the film surface up to 7 T. The magnetization process shows the coexistence of ferromagnetic and paramagnetic contributions at low temperatures, while the typical ferromagnetic magnetization process is mainly observed at high temperatures because of the decrease of the paramagnetic contributions. The observed transport characteristics show a close relation between the magnetism and the impurity conduction. The double exchange mechanism of the Mn-impurity band is one of the possible models for the high-TC ferromagnetism in GaN:Mn.Comment: 20 pages, 4 figures, submitted to Physica

Tracheoesophageal Fistula due to a Damaged Tracheal Stent

We describe the management of a tracheoesophageal fistula due to a damaged tracheal stent, which was first inserted to treat tracheal stenosis. A 29-year-old woman with a history of treated epilepsy had a seizure and suffered from smoke inhalation during a fire. Breathing difficulties appeared and gradually worsened; consultation was obtained two years afterward. After undergoing a thorough examination, the patient was diagnosed with tracheal strangulation. A noncovered, metallic stent was inserted. When the patient was 37 years old, she was admitted to our hospital for the treatment of a tracheoesophageal fistula. We diagnosed it as a tracheoesophageal fistula due to the collapse of the damaged tracheal stent toward the esophageal side, and we decided to perform a mediastinal tracheostomy. Granulation may be formed in the circumference of a stent that has been present for a prolonged period, and removal of the stent may become difficult. This case suggests that insertion of a noncovered, metallic stent is contraindicated for a benign disease