Transcript Slajd 1 - M&oumlssbauer Spectroscopy Division

Magnetyzm i nadprzewodnictwo w EuFe2-xCoxAs2
– badania metodą spektroskopii mössbauerowskiej 57Fe i 151Eu
A. Błachowski1, K. Ruebenbauer1, J. Żukrowski2,
Z. Bukowski3, K. Rogacki3, P.J.W. Moll4, J. Karpinski4, M. Matusiak3
1Laboratorium
Spektroskopii Mössbauerowskiej,
Uniwersytet Pedagogiczny, Kraków, Polska
2Katedra
3Instytut
Fizyki Ciała Stałego, Wydział Fizyki i Informatyki Stosowanej,
Akademia Górniczo-Hutnicza, Kraków, Polska
Niskich Temperatur i Badań Strukturalnych PAN, Wrocław, Polska
4Laboratory
for Solid State Physics, ETH Zurich, Switzerland
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IX Ogólnopolskie Seminarium Spektroskopii Mössbauerowskiej OSSM’2012,
Lublin - Kazimierz Dolny, 10-13 czerwca 2012
Fe-based Superconducting Families
pnictogens: P, As, Sb
chalcogens: S, Se, Te
1111
122
111
11
LnFeAsO(F)
AFe2As2
LiFeAs
FeTe(Se,S)
18 K
15 K
Ln = La, Ce, Pr, Nd, Sm, Gd …
Tc max = 56 K
A = Ca, Sr, Ba, Eu
38 K
Layered Structure of Fe-based Superconductors
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Phase Diagram
Parent Compounds
Ba1-xKxFe2As2
BaFe2-xCoxAs2
BaFe2As2-xPx
Doped Compounds
↓
Superconductors
”122” family of Fe-based superconductors
CaFe2As2
TSDW = 175 K
57Fe
Mössbauer spectra
Relative resistivity
(normalized to the resistivity at 300 K)
versus temperature
A.Błachowski, K.Ruebenbauer, J.Żukrowski,
Z.Bukowski, M.Matusiak, J.Karpinski,
Acta Physica Polonica A 121, 726 (2012)
CaFe1.92Co0.08As2
Tsc = 20 K
57Fe
Mössbauer spectra
BaFe2As2
TSDW = 136 K
Ba0.7Rb0.3Fe2As2
Tsc = 37 K
NM
non-magnetic
Shape of SDW for various temperatures
Square root from the mean squared amplitude of SDW versus temperature
EuFe2As2
Square root from the mean squared amplitude of SDW
versus temperature
TSDW = 192 K
0 = 0.124
A.Błachowski, K.Ruebenbauer, J.Żukrowski, K.Rogacki, Z.Bukowski, J.Karpinski,
Phys. Rev. B 83, 134410 (2011)
EuFe2-xCoxAs2
TN (Eu) = 19 K
A.Błachowski, K.Ruebenbauer, J.Żukrowski, Z.Bukowski, K.Rogacki, P.J.W.Moll, J.Karpinski,
Phys. Rev. B 84, 174503 (2011)
EuFe2-xCoxAs2
57Fe
Mössbauer spectra
TN (Eu) = 19 K
TSDW = 190 K
TSDW = 150 K
TSDW = 100 K
traces of SDW
at 80 K
lack of SDW
Eu2+ Transferred Field on 57Fe
EuFe2-xCoxAs2
57Fe
Mössbauer spectra
Shape of SDW
EuFe1.66Co0.34As2
Square root from the mean squared amplitude of SDW
versus temperature
EuFe2-xCoxAs2
Coconcentration
Tc (K)
T0 (K)
α0
γ
x=0
x = 0.34
192.1(1)
189.1(1)
0.124(1)
0.9(1)
150(2)
140(2)
0.125(9)
0
151Eu
Mössbauer spectroscopy
EuFe2-xCoxAs2
151Eu
Mössbauer spectra
Conclusions
1. The SDW order diminishes in EuFe2-xCoxAs2 with addition of Co, i.e., a transition
temperature is lowered together with the SDW amplitude. Substitution has similar effect on
the SDW shape like temperature, albeit fluctuations are enhanced in comparison with the
temperature effect.
2. SDW survives across the region of superconductivity and it vanishes in the overdoped
region. However, in the region of superconductivity one has some non-magnetic component
with the intensity increasing with the Co-substitution. It seems that superconductivity has
some filamentary character.
3. Eu2+ orders magnetically regardless of the Co-substitution level. Europium moments rotate
from the a-axis in the direction of the c-axis (within a-c plane) with increasing substitution.
Some Eu3+ appears upon substitution with the amount increasing with the increasing Co
concentration. Europium magnetic order and superconductivity coexist in the same volume.
4. Iron experiences a transferred magnetic field from europium for the substituted material – in
the SDW and non-magnetic state both.