Comparison of the low-temperature specific heat of Fe- and Co-doped Bi{sub 1.8}Pb{sub 0.2}Sr{sub 2}Ca(Cu{sub 1{minus}{ital x}}{ital M}{sub {ital x}}){sub 2}O{sub 8} ({ital M}=Fe or Co): Anomolously enhanced electronic contribution due to Fe doping
- Department of Physics, University of Alberta, Edmonton, Alberta, T6G2J1 (CANADA)
Specific-heat data of Fe-doped Bi{sub 1.8}Pb{sub 0.2}Sr{sub 2}Ca(Cu{sub 1{minus}{ital x}}Fe{sub {ital x}}){sub 2}O{sub 8} in the range 2{endash}20 K are presented for {ital x}=1, 2, 4, 6, and 8{percent}. The data are compared with our previous measurements on Co-doped bismuth-strontium-calcium-copper oxide superconductors of nominal composition Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (BISCO 2212). Both Fe and Co are magnetic substitutions with effective moments close to their free-ion value. In the normal state the magnetic susceptibility increases by more than a factor 2 over the doping range due to effective-mass enhancement. In the superconducting state both ions act as magnetic pair breakers. For Co doping the normal-state linear term {gamma} is observed, enhanced due to the effective-mass increase. For Fe doping we observe a large anomalous contribution to the electronic specific heat starting near 15 K and leading at the lowest temperature to a linear term near {gamma}{sub 0}=72 mJ/moleK{sup 2} (1 mole=1 formula unit). The anomalous term is typical of heavy fermion behavior. Comparison with specific-heat data of Co-doped BISCO 2212 suggests that hybridization between 3{ital d} electrons of the dopant and the planar carriers is more effective for Fe doping than for Co doping. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 279814
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 53, Issue 13; Other Information: PBD: Apr 1996
- Country of Publication:
- United States
- Language:
- English
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