Europhys. Lett.
Volume 74, Number 1, April 2006
Page(s) 138 - 144
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 22 February 2006
Europhys. Lett., 74 (1), pp. 138-144 (2006)
DOI: 10.1209/epl/i2005-10491-5

Unconventional superconductivity in $\chem{LaAg_{1-{\it x}}Mn_{\it x}}$: Relevance of spin-fluctuation-mediated pairing

S. N. Kaul1, 2, S. Kumar1, J. Rodríguez Fernández2 and L. Fernández Barquín2

1  School of Physics, University of Hyderabad - Hyderabad - 500 046, India
2  CITIMAC, University of Cantabria - 39005 Santander, Spain

received 11 October 2005; accepted in final form 31 January 2006
published online 22 February 2006

We provide experimental evidence for unconventional superconductivity in a newly synthesized three-dimensional nearly antiferromagnetic metal, $\chem{LaAg_{1-{\it x}}Mn_{\it x}}$, and report results that indicate that the antiferromagnetic spin-fluctuation-mediated pairing may have a direct bearing on this phenomenon. Compared to the heavy-fermion systems, the superconducting transition temperature is nearly 10 times higher, superconductivity is robust against impurities and the specific-heat anomaly associated with the superconducting transition is extremely weak, or even absent. Our results are consistent with certain previously reported theoretical criteria for observing antiferromagnetic spin-fluctuation-mediated superconductivity at elevated temperatures.

74.20.Mn - Nonconventional mechanisms (spin fluctuations, polarons and bipolarons, resonating valence bond model, anyon mechanism, marginal Fermi liquid, Luttinger liquid, etc.).
74.25.-q - Properties of type I and type II superconductors.
74.70.Dd - Ternary, quaternary, and multinary compounds (including Chevrel phases, borocarbides, etc.).

© EDP Sciences 2006