Resistivity, magnetization, and specific heat of YbAgCu{sub 4} in high magnetic fields

Journal Article · Thu Jun 01 04:00:00 EDT 1995 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.51.15053· OSTI ID:54927

Graf, T; Lawrence, J M; Hundley, M F; Thompson, J D ^[1]; Lacerda, A; Haanappel, E; Torikachvili, M S ^[2]; Fisk, Z ^[3]; Canfield, P C ^[4]

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1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2. National High Magnetic Field Laboratory, Pulse Facility, Los Alamos, New Mexico 87545 (United States)
3. Florida State University and National High Magnetic Field Laboratory, Tallahassee, Florida 32306 (United States)
4. 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, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 21 Vol. 51; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
COPPER OXIDES
ELECTRIC CONDUCTIVITY
HIGH-TC SUPERCONDUCTORS
KONDO EFFECT
MAGNETIC FIELDS
MAGNETIC SUSCEPTIBILITY
MAGNETIZATION
MAGNETORESISTANCE
POLYCRYSTALS
SILVER OXIDES
SPECIFIC HEAT
TEMPERATURE DEPENDENCE
YTTERBIUM OXIDES