Ytterbium valence phase transition in Yb/sub x/In/sub 1-//sub x/Cu/sub 2/

Journal Article · Fri May 01 04:00:00 EDT 1987 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.35.6956· OSTI ID:6091199

Felner, I; Nowik, I; Vaknin, D; Potzel, U; Moser, J; Kalvius, G M; Wortmann, G; Schmiester, G; Hilscher, G; Gratz, E; others, and

The recently reported sharp valence phase transition in cubic Yb/sub 0.4/In/sub 0.6/Cu/sub 2/ at T/sub v/approx. =50 K has been studied by a variety of experimental techniques. X-ray diffraction studies from 4.2 to 300 K reveal the cubic Laves phase structure at all temperatures with a jump in the unit-cell size at the transition temperature T/sub v/. Neutron diffraction proves the absence of magnetic order down to 10 K. Magnetic susceptibility data show that the transition temperature T/sub v/ increases when Yb or In are substituted by La, Eu, and Sn and decreases when they are substituted by Y, Lu, and Ga. Moessbauer studies of /sup 170/Yb show that at 4.2 K the Yb ion is nonmagnetic in a cubic environment, whereas at 60 K it is magnetic. Moessbauer studies of /sup 119/Sn exhibit changes in both the spectral area and isomer shift at T/sub v/. Electrical resistivity measurements exhibit a large increase in resistivity at T/sub v/. Specific-heat measurements reveal a characteristic increase of c/sub p/ around T/sub v/. Comparison with Lu/sub 0.4/In/sub 0.6/Cu/sub 2/ behavior yields the increase in entropy due to the valence transition, 13.3(3) J/mole K, in very good agreement with a model calculation of a cubic-split Yb/sup 3+/ and an interconfigurational excitation energy of 220 K. Finally, x-ray-absorption measurements at the Yb L/sub III/ edge reveal a sudden change in the 4f-electron occupancy at T/sub v/ and temperature-independent valences, v(L/sub III/) = 2.9 and 2.8, above and below T/sub v/, respectively.

• Research Organization: Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
• OSTI ID: 6091199
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 35:13; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ABSORPTION SPECTRA
ALLOYS
COHERENT SCATTERING
COPPER ALLOYS
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ENERGY LEVELS
F STATES
INDIUM ALLOYS
LOW TEMPERATURE
MAGNETIC PROPERTIES
MAGNETIC SUSCEPTIBILITY
MEDIUM TEMPERATURE
MOESSBAUER EFFECT
NEUTRON DIFFRACTION
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RARE EARTH ALLOYS
SCATTERING
SPECIFIC HEAT
SPECTRA
THERMODYNAMIC PROPERTIES
ULTRALOW TEMPERATURE
VALENCE
VERY LOW TEMPERATURE
X-RAY DIFFRACTION
YTTERBIUM ALLOYS