Evidence for Fe/sup 4+/ in YBa/sub 2/ (Cu/sub 1-//sub x/M/sub x/)/sub 3/O/sub 7-//sub y/ (M = /sup 57/Fe, /sup 57/Co) by absorption and emission Moessbauer spectroscopy

Journal Article · Thu Dec 01 04:00:00 EST 1988 · Phys. Rev. B: Condens. Matter; (United States)

OSTI ID:6616968

Bottyan, L; Molnar, B; Nagy, D L; Szuecs, I S; Toth, J; Dengler, J; Ritter, G; Schober, J

/sup 57/Fe absorption and /sup 57/Co emission Moessbauer spectroscopy was applied to iron- and cobalt-doped YBa/sub 2/(Cu/sub 1-//sub x/M/sub x/0/sub 3/O/sub 7-//sub y/ high-temperature superconductors (M = /sup 57/Fe, /sup 57/Co; 3.5 x 10/sup -5/less than or equal toxless than or equal to0.1, y = 0 and y = 0.8) between 4.2 and 295 K with and without external magnetic field. four iron species A, B, C, and D, are observed with different dominance at different x and y. Aftereffects of the electron capture are ruled out. At 4.2 K spontaneous antiferromagnetic order is shown by contributions A, B, and C in spectra of samples with x/sub Fe/greater than or equal to0.06. A model-independent separation of the magnetically split subspectra shows an asymmetry parameter of the electric field gradient above 0.8 for A and B. Temperature and external magnetic field dependence of the magnetic splittings is indicative of superparamagnetic relaxation of small clusters. The species A, B, and C are magnetically interrelated. We suggest a preferential Cu(1) substitution by Fe and Co. Three of the four iron species, viz. A, B, and D have been assigned to high-spin Fe/sup 4+/; C is high spin Fe/sup 3+/. We provide evidence that Co is mostly in the four-valent state, too. Four-valent Fe and Co substitution in YBa/sub 2/Cu/sub 3/O/sub 7-//sub y/ is in reasonable agreement with the dopant concentration dependence of T/sub c/. Possible crystallographic assignments of all four iron (cobalt) sites are discussed.

• Research Organization: Central Research Institute for PHysics, H-1525 Budapest, P.O. Box 49, Hungary
• OSTI ID: 6616968
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 38:16; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
BARIUM COMPOUNDS
BARIUM OXIDES
BETA DECAY RADIOISOTOPES
CHALCOGENIDES
COBALT 57
COBALT ADDITIONS
COBALT ALLOYS
COBALT ISOTOPES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
DAYS LIVING RADIOISOTOPES
DOPED MATERIALS
ELECTRON CAPTURE RADIOISOTOPES
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
IRON 57
IRON ADDITIONS
IRON ALLOYS
IRON ISOTOPES
ISOTOPES
LOW TEMPERATURE
MAGNETIC PROPERTIES
MATERIALS
MEDIUM TEMPERATURE
MOESSBAUER EFFECT
NUCLEI
ODD-EVEN NUCLEI
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIOISOTOPES
STABLE ISOTOPES
SUPERCONDUCTORS
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPOUNDS
ULTRALOW TEMPERATURE
VERY LOW TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES