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TT: Tiefe Temperaturen

TT 15: Postersitzung II: Massive HTSL (1-12), Supraleitung: Anwendungen (13-34), Josephsonkontakte und Kryoelektronik (35-75), Elektronenstruktur und Phononen in HTSL (76-79), Schwere Fermionen, Kondo-Systeme (80-99)

TT 15.95: Poster

Mittwoch, 25. März 1998, 15:00–18:30, D

Concentrated Spin-glass like behaviour in the geometrically frustrated pyrochlore Gd₂Mo₂O₇ — •R.K. Kremer¹, N.P. Raju², and W. Schnelle¹ — ¹MPI für Festkörperforschung, Heisenbergstraße 1, D-70569 Stuttgart — ²Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada

The low temperature (0.4 K < <100 K) specific heat of the geometrically frustrated cubic pyrochlore Gd₂Mo₂O₇ has been investigated in magnetic fields up to 14 Tesla. From the comparison with the phonon contribution to the specific heat which were extrapolated from the measurements on nonmagnetic cubic pyrochlores two broad Schottky-like magnetic anomalies are clearly identified. A very strong anomaly in zero - field centered at 10 K contains an entropy of R ln8 and is attributed to concentrated spin-glass like behaviour in the Gd sublattice. With increasing magnetic fields this anomaly is broadened and smeared out and shifted to higher temperatures. A smaller anomaly centered at 75 K which originates from magnetic ordering in the Mo sublattice and which had been detected before only with considerable uncertainty is now clearly resolved. The low - temperature data are compared with a model calculation for a concentrated spin - glass assuming random exchange fields splitting the eightfold degnerated ground state of the spin - only groundstate of Gd³⁺.