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Obsidians from major Ecuadorian sources (outcrops) were analyzed by electron spin resonance, SQUID magnetometry and 57Fe Mössbauer spectroscopy. If the last technique allows to discriminate obsidians from the Quiscatola source, an association of ESR with SQUID magnetometry permits to differentiate obsidians from the sources of Cotopaxi volcano, from the Quiscatola and Mullumica-Callejones sources of the Chacana caldera and to infer that the 12 analyzed obsidians from the pre-Hispanic site of La Maná come from the Mullumica-Callejones source. [ABSTRACT FROM AUTHOR]

New Sr 6 Tb 0.94 Fe 1.06 (BO 3 ) 6 single crystals were obtained from lithium borate high-temperature solution growth under controlled atmosphere. Their average crystal structure was found to adopt the trigonal R-3 space group with lattice parameters a = 12.2164 Å and c = 9.1934 Å. A combined multiscale characterization approach, involving diffuse reflectance, X-ray photoelectron (XPS) and Mössbauer spectroscopies, was undertaken to establish the exact nature of the point defect disorder in this crystal structure. The Fe Tb × antisite disorder in the Sr 6 Tb 0.94 Fe 1.06 (BO 3 ) 6 single crystals is different from the kind of point defect disorder known to exist in the powder phase material counterpart. The absence of Tb 4+ cations in the crystal lattice was established by XPS, and that of any phase transition down to 4 K was checked by specific heat measurements. The magnetic susceptibility curve was found to follow a Curie-Weiss behaviour in the 4–354 K temperature range. [ABSTRACT FROM AUTHOR]

We investigated the structural and magnetic properties of the boride Nd 5 Fe 2 B 6 and of the deuteride Nd 5 Fe 2 B 6 D 4.1 by means of magnetization and specific heat measurements, Mössbauer spectroscopy and neutron powder diffraction. In Nd 5 Fe 2 B 6 D 4.1, deuterium atoms are located in two inequivalent interstitial sites: one octahedral D1 [Nd6] and one tetrahedral D2 [Nd3Fe], both avoiding B as near neighbor. This insertion induces a pronounced anisotropic unit cell expansion along the c -axis. While the Nd 5 Fe 2 B 6 compound exhibits a magnetic ordering below about 68 K, the deuteride exhibits a lower ordering temperature of about 21 K as a consequence of D insertion in the Nd environment. For both compounds powder neutron diffraction investigations have evidenced a ferromagnetic structure with magnetic moments along the c -axis. However, in the deuteride, the Nd magnetic moments values are reduced and that of Fe vanishes. 57 Fe Mössbauer spectroscopy confirms the existence of a small ordered magnetic moment on iron in Nd 5 Fe 2 B 6 and the presence of two environments for Fe in the deuteride. [ABSTRACT FROM AUTHOR]