Upper critical fields and thermally-activated transport of Nd(0.7Fe0.3) FeAs single crystal

Journal Article · Tue Jan 01 00:00:00 EST 2008 · Physical Review. B, Condensed Matter and Materials Physics

OSTI ID:960816

Balakirev, Fedor F ^[1]; Jaroszynski, J ^[2]; Hunte, F ^[2]; Balicas, L ^[2]; Jo, Youn - Jung ^[2]; Raicevic, I ^[2]; Gurevich, A ^[2]; Larbalestier, D C ^[2]; Fang, L ^[3]; Cheng, P ^[3]; Jia, Y ^[3]; Wen, H H ^[3]

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1. Los Alamos National Laboratory
2. NHMFL, FSU
3. CHINA

We present measurements of the resistivity and the upper critical field H{sub c2} of Nd(O{sub 0.7}F{sub 0.3})FeAs single crystals in strong DC and pulsed magnetic fields up to 45 T and 60 T, respectively. We found that the field scale of H{sub c2} is comparable to {approx}100 T of high T{sub c} cuprates. H{sub c2}(T) parallel to the c-axis exhibits a pronounced upward curvature similar to what was extracted from earlier measurements on polycrystalline samples. Thus this behavior is indeed an intrinsic feature of oxypnictides, rather than manifestation of vortex lattice melting or granularity. The orientational dependence of H{sub c2} shows deviations from the one-band Ginzburg-Landau scaling. The mass anisotropy decreases as T decreases, from 9.2 at 44K to 5 at 34K. Spin dependent magnetoresistance and nonlinearities in the Hall coefficient suggest contribution to the conductivity from electron-electron interactions modified by disorder reminiscent that of diluted magnetic semiconductors. The Ohmic resistivity measured below T{sub c} but above the irreversibility field exhibits a clear Arrhenius thermally activated behavior over 4--5 decades. The activation energy has very different field dependencies for H{parallel}ab and H{perpendicular}ab. We discuss to what extent different pairing scenarios can manifest themselves in the observed behavior of H{sub c2}, using the two-band model of superconductivity. The results indicate the importance of paramagnetic effects on H{sub c2}(T), which may significantly reduce H{sub c2}(0) as compared to H{sub c2}(0) {approx}200--300 T based on extrapolations of H{sub c2}(T) near T{sub c} down to low temperatures.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 960816
• Report Number(s): LA-UR-08-07326; LA-UR-08-7326; TRN: US1002639
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 78; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ACTIVATION ENERGY
ANISOTROPY
CRITICAL FIELD
CUPRATES
ELECTRON-ELECTRON INTERACTIONS
FLUORINE COMPOUNDS
IRON ARSENIDES
MAGNETIC FIELDS
MAGNETIC SEMICONDUCTORS
MAGNETORESISTANCE
MONOCRYSTALS
NEODYMIUM COMPOUNDS
SCALING
SPIN
SUPERCONDUCTIVITY
TEMPERATURE RANGE 0065-0273 K
TRANSPORT