1. Special Romp session, LT25
8th Aug. 2008, Amsterdam
75As-NMR study of BaFe2As2
H. Fukazawa1, N. Takeshita2, T. Yamazaki1, K. Kondo1,
K. Hirayama1, Y. Kohori1, K. Miyazawa2,3,
H. Kito2, H. Eisaki2, and A. Iyo2
1Department of Physics, Chiba University, Chiba, Japan
2Nanoelectronics Research Institute, National Institute
of Advanced Industrial Science and Technology, Tsukuba, Japan
3Department of Applied Electronics, Tokyo University of Science, Noda
H. Fukazawa et al.: to be published in J. Phys. Soc. Jpn. (2008).
; arXiv: v3.
Pressure study; arXiv: v1.
1. Magnetic order in BaFe2As2
2. Pressure effect on BaFe2As2

2. Discovery of superconductivity Next parent compoundsAs Fe
Ba(K)
O(F) As Fe La
FeAs layer
FeAs layer
Y. Kamihara et al.: J. Am. Chem. Soc. 130 (2008) 3296.
M. Rotter et al.: arXiv: v1.

3. P induced superconductivity ??
P. L. Alireza et al.:
arXiv
M. S. Trikachivili et al.:
arXiv v1.
P induced superconductivity ??

4. 75As NMR spectrum of BaFe2As2
Typical powder-pattern spectrum
expected for weak
electric quadrupole interaction
Estimated 75As NQR frequency
nQ = 2.2 MHz:
much smaller than nQ’s of
superconducting oxypnictides
(nQ ~ 9-12 MHz)
H.-J. Grafe et al.: PRL 101 (2008)
H. Mukuda et al.: arXiv: v1.
Partial orientation of powders:
Hext parallel to ab plane
G. C. Carter et al.: Metallic Shifts in NMR
(Pergamon Press, Oxford etc., 1977) Chap. 2&6.

5. 75As NMR spectra at various T
Spectral broadening below 130 K
SDW magnetic ordering
(TSDW = 131 K in our samples)
Much oriented powder: sharper
Mag. easy axis: within ab plane
Hint // c axis
Hint
Q. Huang et al.:
arXiv: v1.

6. FWHM & FWQM vs T 4.2 K < T < TSDW FWHM: nearly T independent
FWQM: gradual decrease
T ~ TSDW
FWHM&FWQM:
sudden decrease
from finite DB to 0 T
The SDW anomaly in BaFe2As2
is likely of the first order.

7. Zero external field 75As NMR spectrum
Hint
・Hint at the As site is about 1.4 T.
・The magnetically ordered state is
formed with the commensurate q vector.
(consistent with q =(1,0,1) in ND)
Hint
Q. Huang et al.:
arXiv: v1.

8. Pressure effect on BaFe2As2
SDW anomaly is suppressed
by applied P, but is
simultaneously robust against P.
P induced SC in BaFe2As2 ??
-no zero resistivity-

9. Pressure effect on oxypnictides/pnictides
Mini cubic anvil apparatus
Bridgman anvil cell
63Cu NQR
- Cu2O -
See also r (P,T ) of NdFeAsO0.6
N. Takeshita et al.: JPSJ 77 (2008)
H. Fukazawa et al. : RSI 78 (2007)
K. Hirayama et al. : JPSJ 77 (2008)
Not only doping study but also pressure study
of the pnictides has a strong impact
upon this study field.
We can perform NMR/NQR
under such high pressure
of 10 GPa!