1. Magnetic, structural and electronic properties of LaFeAsO1-xFx
Rüdiger Klingeler
Leibniz Inst. for Solid State and Materials Research IFW Dresden
Today:
Original Abstract:
NMR
mSR, M, r
Pulsed field
m-wave, M
Optics
Neutrons
Magnetisation
H. Grafe et al., PRL 101, (‘08)
H.H. Klauss et al., PRL, in print
H. Luetkens et al., PRL, accepted
G. Fuchs et al., PRL, accepted
A. Narduzzo et al., Phys. Rev. B, in print
S.-L. Drechsler et al., arXiv:
H. Luetkens et al., arXiv:
S.A.J. Kimber et al. arXiv:
R. Klingeler et al., arXiv:

2. Our samples
non-magnetic
H. Luetkens et al., arXiv:

3. LaFeAsO1-xFx
C. Hess et al.

4. LaFeAsO1-xFx c(T) ~ T: AFM correlations? Sample degrades >500K
R. Klingeler et al., arXiv:

5. LaFeAsO1-xFx c(T) ~ T: pseudogap vs. AFM correlations
Slope dc/dT const.
AFM correlations in SC samples
or: x-independent large pseudogap
R. Klingeler et al., arXiv:

6. LaFeAsO1-xFx c(T) ~ T: pseudogap vs. AFM correlations
Slope dc/dT const.
AFM correlations in SC samples
or: x-independent large pseudogap
R. Klingeler et al., arXiv:

7. PrFeAsO: Thermal Expansion

8. PrFeAsO: Thermal Expansion
La  Pr
Field dependent structural changes below TN
(no field effect in LaFeAsO)

9. Acknowledgements Cooperations: H.H. Klauss et al. TU Dresden
B. Büchner
Synthesis: G. Behr, J. Werner, M. Deutschmann, R. Müller, R. Pichl, …
Theory: S.L. Drechsler, H. Eschrig, K. Koepernick, ….
Transport : A. Kondrat, C. Hess et al.
M, Thermodynamics: N. Leps, S. Gass, L. Wang et al.
NMR: H. Grafe, G. Lang, D. Paar, V. Kataev et al.
Diffraction: J. Hamann-Borrero
Pulsed field: G. Fuchs et al.
Microwave absorption: A. Narduzzo et al.
Cooperations: H.H. Klauss et al. TU Dresden
J. Litterst et al TU Braunschweig
H. Luetkens et al. PSI Villingen
A. de Visser et al. U Amsterdam
M. Braden et al. U Köln
I. Eremin et al. MPI PKS Dresden
A. Vassiliev et al. Moscow State University

11. LaFeAsO: Pressure dependence
Negative
p-dependence of TN
Coll.: M. Braden, U Köln
A. De Visser, U. Amsterdam

12. Transport Resistivity Clearly two features in the second derivative
Check with Christian
T_dep something astonishingly similar to cuprates
Clearly two features in the second derivative
Anomaly at T = 150 K survives for x = 0.05
~T2, ~T depending on doping and temperature

13. Susceptibility Phase Transition
Kink around 140 K due to afm correlations
Derivative shows two peak structure (magnetic and structural phase transition)
Shift towards lower energies
Decreasse of magnetization at the kink

14. Mößbauer/ZF-mSR Clear oscilations below TN Clear line splitting at TN
AFM arises from a spin density wave of the conduction electrons
Clear line splitting at TN
Effective moment m=0.25mB << 2

15. mSR TF mSR, x = 0.1 ZF mSR, x = 0.1 Magnetism suppressed
Relaxation rate s ~ l-2 ~ n/m* → lab(0) = 254 nm

16. Spin lattice relaxation
NMR
75As, LaO0.9F0.1FeAs
Knight shift
Spin lattice relaxation
Knight shift: 1) Pseudogap-like density suppression
2) Spin-singlet pairing
T1-1 ~ T3 for T < Tc → line nodes

17. LaFeAsO1-xFx Weak localization-like behavior at low T for x<0.05
Superconductivity for x>0.04
Anomaly at T = 150 K for nonsuperconducting samples
Maximum above Tc for sc samples remnant from upturn
Change from linear T-dependence in the normal state to quadratic
Tc decreases for high doping
C. Hess et al.

18. LaFeAsO1-xFx
R. Klingeler et al., arXiv: