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Shigeki Fujiyama Dept. of Applied Physics, University of Tokyo, Japan CREST-JST

Microscopic estimation of antiferromagnetic correlation between p -electrons and d -local moments in FISC k -(BETS) 2 FeBr 4. Shigeki Fujiyama Dept. of Applied Physics, University of Tokyo, Japan CREST-JST J. Kikuchi, M. Takigawa, K. Kanoda, H-B. Cui,

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Shigeki Fujiyama Dept. of Applied Physics, University of Tokyo, Japan CREST-JST

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  1. Microscopic estimation of antiferromagnetic correlation between p-electrons and d-local moments in FISC k-(BETS)2FeBr4 Shigeki Fujiyama Dept. of Applied Physics, University of Tokyo, Japan CREST-JST J. Kikuchi, M. Takigawa, K. Kanoda, H-B. Cui, H. Kobayashi, H. Fujiwara, E. Fujiwara

  2. π 2D π conduction layer d magnetic anion layer π 2D π conduction layer 2 dim. correlation and p-d interactions BETS S=5/2 FeX4- (X=Br, Cl) l-type k-type

  3. k AF SC 1.0 R (Ohm) 6 Resistivity of k-(BETS)2FeBr4 Zero magnetic field Under magnetic field Ectronic conduction in 2 dim molecular layer survives even in the antiferromagnetic state FISC at 12.5 T T < 0.3 K

  4. Electronic phase diagram of k-ET T Para metal Mott AF SC 1/UD(eF) Why p-d in k- ET(related) material? k-(BETS)2MeX4: Metal with AF fluctuation

  5. In this talk • 77Se NMR sepctra/frequency shifts ofk-(BETS)2FeBr4single Xtal in the paramagnetic state are presented. • p-d magnetic interaction J is estimated. • Strong antiferromangetic correlation is demonstrated by 1/T1T.

  6. 77Se NMR spectra 4 independent Se sites are observed along H//b.

  7. Local field at molecules J H0 Fe dipole

  8. Linear relation against fields constant at low T

  9. Estimation of isotropic transfer B The transfer from anions to the internal core electrons at Se sites are isotropic. This term is nothing to do with the local field at HOMO electrons.

  10. Cancellation of local fields Apcp/NAmB=-.04%~0.39% J=-24[kOe/mB] = -8 K Independent of Se sites Isotropic.

  11. Temperature dependence of the Knight shift Uniform susceptibility is dominated by local d spins. Temperature dependence of c well follows Brillouin function. Significant variation in cp due to Fe spin is not observed. Apcp/NAmB=-.05%〜0.53% J=-25[kOe/mB] = -8 K

  12. TRKKY TK QCP Heavy Fermion AF Jcf/W CeNi CeSn3 CeRu2Si2 CeCu2Si2 CeAl3 CeIn3 CeAl2 CeB6 CeCu6 Towards magnetic instability RKKY Kondo screening Theoretical Quantum Critical Point at Jcf~W J(~8K)<<W(~1eV) : RKKY limit Anisotropic d spin

  13. Strong antiferromagnetic correlation

  14. Conclusion The Hex dependence at 1.5 K and T dependence at 15.5 T of the frequency shifts well follows a model assuming molecular field approximation. Significant modulation of cp is not observed. Internal magnetic fields on the molecules are canceled at about 12 T, where FISC is observed. Isotropic antiferromagnetic p-d correlation is microscopically estimated as J=-24 [kOe/mB]. Strong antiferromagnetic correlation is observed by 1/T1.

  15. Para 1/U Mott SC ? QCP Jpd Challenge of p-d interaction in vicinity of Mott transition

  16. Reduction of Linewidth

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