Resistivity, magnetization, and specific heat of YbAgCu{sub 4} in high magnetic fields
- Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
- National High Magnetic Field Laboratory, Pulse Facility, Los Alamos, New Mexico 87545 (United States)
- Florida State University and National High Magnetic Field Laboratory, Tallahassee, Florida 32306 (United States)
- Ames Laboratory, Ames, Iowa 50011 (United States)
We report measurements of the resistivity {rho}, Sommerfeld coefficient of specific heat {gamma}, and magnetization {ital M} of polycrystalline YbAgCu{sub 4} in high magnetic fields 0{le}{ital B}{le}18 T [in the case of {ital M}({ital B}) to 50 T]. A comparison of the temperature-dependent susceptibility {chi}({ital T}) as well as field-dependent Sommerfeld coefficient {gamma} and magnetization to Kondo theory for a {ital J}=7/2 impurity shows that theory correctly predicts the functional dependence of these quantities on {ital T} and {ital B}, but the characteristic temperatures determined from the various measurements (120, 98, 77, and 63 K) differ by nearly a factor of 2, which is difficult to understand within the context of Kondo theory even when other possible contributions are considered. In addition the normalized (Wilson) ratio of {chi} to {gamma} is 1.00 at zero field (compared to 1.14 in Coqblin-Schrieffer theory) and decreases with increasing magnetic field. The magnetoresistance is positive at all temperatures, reaching a value {Delta}{rho}({ital B})/{rho}({ital B}=0)=0.6 at 25 mK and 18 T. The low-temperature magnetoresistivity {Delta}{rho}({ital B}) varies as {ital B}{sup 1.5}. We argue that this is dominated by an ordinary impurity effect. Kohler`s rule is clearly violated as the temperature is raised; the scattering rate appears to increase with field below 40 K and decrease with field above 40 K. This behavior is expected for an Anderson lattice when a pseudogap is present. At low temperature the resistivity increases as {ital AT}{sup 2}. The coefficient {ital A} (corrected for cyclotron-orbit effects) increases with field such that the ratio {ital A}({ital B})/{gamma}({ital B}){sup 2} is a constant. Doping with Lu onto the Yb site, or with Ni onto the Cu site, changes the magnitude of the low-temperature resistivity in a manner consistent with the predictions of the theory of ligand-induced disorder in an Anderson lattice.
- OSTI ID:
- 54927
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 51, Issue 21; Other Information: PBD: 1 Jun 1995
- Country of Publication:
- United States
- Language:
- English
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