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