Experimental probing of exchange interactions between localized spins in the dilute magnetic insulator (Ga,Mn)N

The sign, magnitude, and range of the exchange couplings between pairs of Mn ions is determined for (Ga,Mn)N and (Ga,Mn)N:Si with x < 3%. The samples have been grown by metalorganic vapor phase epitaxy and characterized by secondary-ion mass spectroscopy; high-resolution transmission electron microscopy with capabilities allowing for chemical analysis, including the annular dark-field mode and electron energy loss spectroscopy; high-resolution and synchrotron x-ray diffraction; synchrotron extended x-ray absorption fine-structure; synchrotron x-ray absorption near-edge structure; infra-red optics and electron spin resonance. The results of high resolution magnetic measurements and their quantitative interpretation have allowed to verify a series of ab initio predictions on the possibility of ferromagnetism in dilute magnetic insulators and to demonstrate that the interaction changes from ferromagnetic to antiferromagnetic when the charge state of the Mn ions is reduced from 3+ to 2+.Comment: 12 pages, 14 figures; This version contains the detailed characterization of the crystal structure as well as of the Mn distribution and charge stat

Rare suprasellar glioblastoma: report of two cases and review of the literature

BACKGROUND AND IMPORTANCE: The suprasellar and hypothalamic/chiasmatic regions can harbor a broad range of pathologic conditions, both neoplastic and nonneoplastic; however, malignant gliomas are extremely rare in those regions. CLINICAL PRESENTATIONS: Patient 1 was a 70 year-old man with weight loss and rapidly progressive visual impairment. A mass centered in the hypothalamus was detected on magnetic resonance (MR) imaging. The second patient, a 45 year-old woman, complained of visual symptoms and headaches. MR imaging revealed a combined intra- and suprasellar mass. In both instances, the preoperative differential diagnosis favored craniopharyngioma. Histological examination confirmed the diagnosis of glioblastoma. CONCLUSION: We report two rare adult cases of hypothalamic/chiasmatic glioblastoma. The authors review the literature, highlighting the importance of considering this rare entity in the differential diagnosis of suprasellar and hypothalamic lesions