This document discusses the interaction between magnetism and superconductivity. It describes different types of magnetism like ferromagnetism and diamagnetism. It also discusses the basics of superconductivity and how a superconducting state can be induced by a magnetic field. The document then focuses on the iron-based superconductor KxFe2-ySe2, including its crystal growth process and characterization techniques used to study it like X-ray diffraction and magnetization. It aims to understand how the different phases in KxFe2-ySe2 interact individually and with each other, and why high-temperature superconductors form.

1. Interaction Between
Magnetism and
Superconductivity
Jeremie Doehla
Adviser: Dr. Goran Karapetrov
Department of Physics
Drexel University
June 4, 2013

2. Magnetism
Ferromagnetism
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Spontaneous spin
alignment
Long range order
Diamagnetism
●
●
Negative magnetic
susceptibility
Perfect diamagnetism
= Meissner effect

3. Superconductivity
●
Perfect diamagnet
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Long range order
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BCS theory
–
Low temperature
–
Absence of
magnetic field
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Type I
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Type II – vortex state

4. Free Energy (F)
FerromagneticSuperconductor Hybrids
Applied Magnetic Field
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A superconducting state may be induced by a
magnetic field.

5. Proximity Effect
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When in contact with a
normal or ferromagnetic
material there is a
penetration of the
cooper pairs into
said material.
Ginzburg-Landau
Equation:

6. KxFe2-ySe2
FeSe
●
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New materials
(2008)
Each phase may have
a different magnetic
order
1 phase found to be
superconducting
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KFe2Se2-z
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K2Fe4Se5
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Two structures of
KFe2Se2
(different charge
orderings)
And Others
KFe2Se2

7. KxFe2-ySe2: Crystal Growth
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●
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Step 1: FeSe
(vapor self transport)
Step 2: KFe2Se2
(from melt)
Post annealing/
quenching
Contamination
concerns

8. KxFe2-ySe2: Characterization
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Why is it a
superconductor?
How do the different
phases interact with
each other and
behave
independently?
Techniques:
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X-Ray Diffraction
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Resistance
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Hall effect
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Magnetization

9. Characterization
X-Ray diffraction:
●
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Crystal structure
characterization
Different crystal
phases will have
different
characteristic
peaks
Resistivity:
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●
CDW
Varies greatly
with
stoichiometry

10. Characterization
Hall Effect
●
●
Charge carrier
FeSe has been found to
have a change in the
sign of the hall effect
Magnetization
●
Hc1, Hc2, magnetic
susceptibility

11. Conclusion
KxFe2-ySe2
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●
In General
Behavior of each phase
individually
●
Interaction between the
different phases
●
Why high temperature
superconductors form
Further investigate
the fundamental
relationship between
magnetization and
superconductivity

12. References
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Ashcroft and Mermin. Solid State Physics. Brooks, Belmont, CA, 1976.
A. I. Buzdin. Proximity eects in superconductor-ferromagnet heterostructures. Reviews of modern physics, 77, July
2005.
T.-L. Xia D. M. Wang, J. B. He and G. F. Chen. Eect of varying iron content on the transport properties of the
patassium-intercalated iron selenide k(x)fe(2-y)se(2). Physical Review B, 83, 2011.
Bing Shen Zhen-yu Wang Chun-Hong Li Fei Han, Huan Yang and Hai-Hu Wen. Metastable superconducting state in
quenched k(x)fe(2-y)se(2). Philosophical Magazine, 92, July 2012.
Kuo-Wei Yeh Ta-Kun Chen Tzu-Wen Huang Phillip M.Wu Yong-Chi Lee Yi-Lin Huang Yan-Yi Chu Der-Chung Yan FongChi Hsu, Jiu-Yong Luo and Maw-Kuen Wu. Superconductivity in the pbo-type structure alpha-fese. Proceedings of
the National Academy of Sciences, 105(38), September 2008.
M. Decroux-O. Fischer G. Remenyi H. W. Meul, C. Rossel and A. Briggs. Observation of magnetic-eld-induced
superconductivity. The American Physical Society, 53(5), July 1984.
V. Jaccarino and M. Peter. Ultra-high-eld superconductivity. Physical Review Letters, 9(7), October 1962.
Genda Gu J M Tranquada Jinsheng Wen, Guangyong Xu and R J Birgeneau. Interplay between magnetism and
superconductivity in iron-chalcogenide superconductors: crystal growth and characterizations. Reports on Progress
in Physics, 74, September 2011.
Hirano Kamihara, Watanabe and Hosono. Iron-based layered superconductor la[o(1-x)f(x)]feas(x = 0.05-0.12).
Journal of the American Chemical Society, 130, March 2008.
Charles Kittel. Introduction to Solid State Physics. John wiley and Sons, Inc., USA, 2005.
I. F. Lyuksyutov and V. L. Pokrovsky. Ferromagnet-superconductor hybrids. Advances in Physics, 54(1), 2005.
Ksenofontov Felser Xu Zandbergen Hor Allred Williams Qu Checkelsky Ong McQueen, Huang and Cava. Extreme
sensitivity of superconductivity to stoichiometry in fe1+delta se. Physical Review B, 79, January 2009.
Davin J. Morgan and J. B. Ketterson. Asymmetric ux pinning in a regular array of magnetic dipoles. Physical Review
Letters, 80(16), April 1998.
A.C. Rose-Innes and E.H. Rhoderick. Introduction to Superconductivity. Pergamon Press Ltd., Elmsford, New York,
1978.
T. Terashima T. Yakabe Y. Terai M. Tokumoto A. Kobayashi H. Tanaka S. Uji, H. Shinagawa and H. Kobayashi.
Magnetic-eld-induced superconductivity in a two-dimensional organic conductor. Letters to nature, 410, April 2001.
Applied Superconductivity and Cryoscience Group. Lectures on superconductivity. Technical report, University of
Cambridge.
S. H. Yu S. Avci Z. L. Xiao H. Claus J. Schlueter V. V. Vlasko-Clasov U. Welp U. Patel, J. Hua and W. K. Kwok. Growth
and superconductivity of fese(x) crystals. Applied Physics Letters, 94, 2009.
Zhi Li Peng Deng Kai Chang Ke He Shuaihua Ji Lili Wang Xucun Ma Jiang-Ping Hu Xi Chen Wei Li, Hao Ding and QiKun Xue. Kfe(2)se(2) is the parent compound of k-doped iron selenide superconductors. Physical Review Letters,
109, 2012.

13. Acknowledgments
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Petra Husanikova
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Christopher Brown
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Joey Lambert
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Erica Smith

14. Sample carrier design
●
Needs to fit down the
central shaft of dewar
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Space considerations
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Thermal considerations
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Vacuum considerations
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Electrical contacts
–
–
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Sensors
Utility
Replaceable parts

15. Sample carrier design
●
Still a work in progress
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Temperature sensor
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Heating
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Electrical leads

16. Crystal Growth and
Measurements done
(although, not related to KxFe2-xSe2)
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CuxTiSe2
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Iodine vapor transport
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Grown on Temple's
campus
Measurements:
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Resistance vs.
temperature
Resistance
measured
(same place we will grow
KxFe2-xSe2)
Temperature (K)