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TT: Tiefe Temperaturen
TT 25: Correlated Electrons - Poster Session
TT 25.118: Poster
Mittwoch, 29. März 2006, 14:30–18:30, P1
Quantum phase transitions in Nb1−yFe2+y — •Manuel Brando, Dennis Moroni-Klementowicz, Carsten Albrecht, William Duncan, and F. Malte Grosche — Dept. of Physics, Royal Holloway, University of London, Egham TW20 0EX, UK
The C14 Laves phase NbFe2 is a rare example of low temperature spin density wave order (SDW, TN≃ 10 K) among the d-metal compounds. Magnetic ordering, which is inferred from magnetic, thermodynamic and magnetoresistive signatures, as well as historic NMR and µSR data, emerges out of a nearly ferromagnetic state with a Stoner enhancement factor of about 150, and is easily suppressed by surprisingly low critical fields µ0 Hc ≃ 0.2−0.6 T.
The low temperature state of NbFe2 can be tuned by slightly modifying the stoichiometry within the narrow Nb-Fe homogeneity range. To the Nb-rich side, a quantum critical point is approached for y≃ 0.008, characterised by non-Fermi liquid temperature dependences of heat capacity and resistivity. On the Fe-rich side, however, the SDW state observed in stoichiometric NbFe2 appears to transform continuously into ferromagnetic ordering for y>0.01.
We present low temperature magnetic, thermodynamic and transport measurements at ambient and high hydrostatic pressure, taken on samples across the homogeneity range, in order to elucidate the unusual magnetic phase diagram of NbFe2. The findings are discussed within the working hypothesis that stoichiometric NbFe2 forms low-Q, long wavelength magnetic order, which transforms continuously towards ferromagnetism (Q=0) on increasing Fe content.