NMR investigation of rapid structural changes and non-metal-to-metal transition in the molten eutectic Ge–Te alloy

• Published in: Journal of non-crystalline solids Vol. 353; no. 32-40; pp. 3384 - 3388
• Main Authors: Tsuchiya, Y., Narita, M., Kanaya, H., Kurokawa, K.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15-10-2007; Elsevier
• Subjects: Chalcogenides; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electrical and electronic properties; Electron states; Electronic structure of liquid metals and semiconductors and their alloys; Exact sciences and technology; Liquid alloys and liquid metals; Liquid metals and alloys; Magnetic properties; Magnetic resonances and relaxations in condensed matter, mössbauer effect; NMR, MAS–NMR and NQR; Nuclear magnetic (and quadrupole) resonance; Nuclear magnetic resonance and relaxation; Phases and equilibria; Physics; Structure; Structure of solids and liquids; crystallography; Studies of specific liquid structures; Chalcogenides; Liquid alloys and liquid metals; 75.01.A; Phases and equilibria; Electrical and electronic properties; Nuclear magnetic (and quadrupole) resonance; NMR, MAS–NMR and NQR; Structure; Magnetic properties; Liquid state; Localized states; Liquid alloys and liquid metals; Electrical and electronic properties; Chalcogenides; Magnetic properties; Nuclear magnetic (and quadrupole) resonance; Phases and equilibria; NMR; Phase transformations; Metal non metal transition; Spin-spin relaxation; High temperature; Electronic density of states; MAS-NMR and NQR; Structure; Supercooled liquids; Temperature effects; Spin-lattice relaxation; Germanium tellurides; Eutectic alloys; Nuclear magnetic resonance; Liquid structure; Melts
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2007.05.120

Resonance shift, K125, spin-lattice relaxation time, T1 and spin–spin relaxation time, T2 for 125Te nuclei in molten Ge15Te85 and Te in deeply under-cooled state have been measured as a function of temperature. The temperature dependence of K125 is compared with that of the extent of structural change, C, and it is shown that the rapid increase of K125 with increasing temperature can be attributed to an increase of the density of states at the Fermi level proportional to the extent of structural change. At high temperatures, the dependences on the temperature of K125 and T1 conform to the Korringa relation with an enhancement factor or the relaxation mechanism expected metallic nature. At low temperatures, in contrast, the Redfield theory assuming localized spins of which the density is proportional to C can explain the overall temperature dependences of T1 and T2. These results provide the first clear evidence for a crossover transition from extended to localized states in the electron system accompanying the rapid structural changes.