Europhys. Lett.
Volume 63, Number 6, September 2003
Page(s) 860 - 866
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 November 2003
DOI: 10.1209/epl/i2003-00599-0
Europhys. Lett., 63 (6) , pp. 860-866 (2003)

Field tuning of the electron and hole populations in the ruthenate $\chem{Bi_3Ru_3O_{11}}$

Wei-Li Lee1, M. K. Haas2, G. Lawes3, A. P. Ramirez3, R. J. Cava2, 4 and N. P. Ong1, 4

1  Department of Physics, Princeton University - Princeton, NJ 08544, USA
2  Department of Chemistry, Princeton University - Princeton, NJ 08544, USA
3  Los Alamos National Laboratory - Los Alamos, NM 87544, USA
4  Princeton Materials Institute, Princeton University - Princeton, NJ 08544, USA

(Received 15 May 2003; accepted in final form 4 July 2003)

Experiments on the Hall coefficient $R_{\ab{H}}$ and heat capacity C reveal an unusual, compensated electronic ground state in the ruthenate $\chem{Bi_3Ru_3O_{11}}$. At low temperature T, $R_{\ab{H}}$ decreases linearly with magnetic field |H| for fields larger than the field scale set by the Zeeman energy. The results suggest that the electron and hole populations are tuned by H in opposite directions via coupling of the spins to the field. As T is decreased below 5 $\un{K}$, the curve C(T)/T vs. T2 shows an anomalous flattening consistent with a rapidly growing Sommerfeld parameter $\gamma(T)$. We discuss shifts of the electron and hole chemical potentials by H to interpret the observed behavior of $R_{\ab{H}}$.

72.15.-v - Electronic conduction in metals and alloys.
72.60.+g - Mixed conductivity and conductivity transitions.
71.27.+a - Strongly correlated electron systems; heavy fermions.

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