pascoal g. pagliuso grupo de propriedades Ópticas e magnéticas dos sólidos (gpoms)
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Workshop on Digital Design of Materials - 09/2013. Routes for finding superconductors based on structural trends. Pascoal G. Pagliuso Grupo de Propriedades Ópticas e Magnéticas dos Sólidos (GPOMS) Instituto de Física ``Gleb Wataghin'', UNICAMP – Campinas -SP. UC - Irvine. CBPF. Outline. - PowerPoint PPT PresentationTRANSCRIPT
Pascoal G. PagliusoPascoal G. PagliusoGrupo de Propriedades Ópticas e Magnéticas dos Sólidos (GPOMS)Grupo de Propriedades Ópticas e Magnéticas dos Sólidos (GPOMS)Instituto de Física ``Gleb Wataghin'', UNICAMP – Campinas -SPInstituto de Física ``Gleb Wataghin'', UNICAMP – Campinas -SP
CBPFUC - Irvine
Workshop on Digital Design of Materials - 09/2013
Routes for finding superconductors based on structural trends
Outline
I. HFS in similar crystal structures
II. The role of dimensionality and crystal structures
(CEF – single ion anisotropy)
III. Possible relationship with FeAs-based intermetallic
IV. The role of local distortion of FeAs bonds
V. Substitution effects on the localization character
and orbital degrees of freedom of the Fe 3d bands
VI. Implications in new materials search
and suggestions for digital design
0.0 0.2 0.4 0.6 0.8 1.0
0.5
1.0
1.5
2.0
2.5
3.0
SG
TN(cp) TG(SR) TC()
X
AFM
T * (K
)
SC
CemMnIn3m+2n
Ce2Rh1-xIrxIn8 [3,4,5]CeRh1-x(Ir,Co)xIn5 [1,2]
[1] Pagliuso et al, Physica B, 312, 129 (2002).[2] Pagliuso et al, Phys.Rev B, 64, 100503(R) (2001).
[3] E.N. Hering et al Physica B, 378, 423 (2006). [4] E.N. Hering, Physica B, 403, 780 (2008);[5] E. N. Hering, C. Adriano, et al, PRB (2011).
-Ce2CoIn8
TC 1.0 K
600 mJ/K2 mole Ce
c/a as control parameter for Tc
Is there an intrisic parameter in this plot, which depends on
c/a and determines TC?
P.G. Pagliuso et al. PRB, 100503 (R) (2002); Physica B 312-313, 129 (2002).
Tuning:-JRKKY
- TK
- CEF
TN evolution for RmAnIn3m+2n(m = 1,2 ; n =0,1)
P.G. Pagliuso et al. Physical Review B. 62, 12266 (2000) also PRB 2001.
RE moments ordered alongc-axis.
RE moments in the ab-plane.
Garcia, E. Miranda, et al. JAP (2006)
INS and XAS CEF study in Ce-M-In
T. Willers et al.
A. Severing et al. PRB (2010)A.D. Christianson et al PRB (2004).
Extrapolation of CEF trend to Ce-based materials
TRKKY
TK
TN
(increasing of g-anisotropy)
Frustrated local moments + hybridization
Strong magnetic-fluctuations??
isotropic
cubic
anisotropic anisotropic anisotropic
tetragonal
1-1-5 – FeAs-intermetallics ?
M. S. Torikachvilli et al. PRB 2008. Marianne Rotter al. New J. of Phys. (2009).
11
FeAs-based superconductors✤ Common Structural parameter: FeAs4 tetrahedral
✤ Common Electronic parameter: SDW magnetic instability
J. Paglione and R. L. Greene. Nature Physics 6, 645 (2010).
E. Granado et al. PRB 83, 184508 (2011)
Resultados – EXAFS
Site specific ESR on Fe-based Intermetallic Compounds
Ho g-value or IT H relaxation and inhomogeneity
I (T)
ESR Results
P. F. S. Rosa et al. PHYSICAL REVIEW B 86, 165131 (2012)P. F. S. Rosa et al. submitted to PRL (2013).
Eu 2+
ESR - Results
P. F. S. Rosa et al. PHYSICAL REVIEW B 86, 165131 (2012)P. F. S. Rosa et al. submitted to PRL (2013).
xy
z
xy
z
Smaller dFe-As with chemical substitution, hydrostatic pressure and magnetic field in the plane!
xy occupation increases
SDW Phase vanishes
Implications for designing materials
•Quasi 2-d helps a lot; maybe not much 2-d needed – increase c/a – tune CEF GS
•Need bigger bandwidths to increase Tsf, but keep optimized Tc/Tsf - 3d spins in the active layer.
• To increase TC for magnetically mediated SC:Tsf, characteristic T for spin fluctuations highTunable carrier density
1-1-5 e 2-1-8 1-2-2 2-1-4, etc
Examples for Digital Design?
1) Bi2CuIn8
3d single band at FS? Which symmetry? 2) CaFeSn5
Fe 3d T2g at the Fermi level?dxy with larger occupation? 3) Yb2CoAs4
Yb3+GS Ising like?Energy scale of 4-electrons?
2-1-8 1-2-2 2-1-4