Interaction Between Magnetism and

Superconductivity

Jeremie Doehla

Adviser: Dr. Goran Karapetrov

Department of Physics

Drexel University

June 4, 2013

Magnetism

Ferromagnetism● Spontaneous spin

alignment

● Long range order

Diamagnetism● Negative magnetic

susceptibility

● Perfect diamagnetism = Meissner effect

Superconductivity

● Perfect diamagnet

● Long range order

● BCS theory

– Low temperature

– Absence of magnetic field

● Type I

● Type II – vortex state

Ferromagnetic-Superconductor Hybrids

● A superconducting state may be induced by a magnetic field.

Applied Magnetic Field

Fre

e E

nerg

y (F

)

Proximity Effect

● When in contact with a normal or ferromagnetic material there is a penetration of the cooper pairs into said material.

● Ginzburg-Landau Equation:

KxFe

2-ySe

2

● New materials (2008)

● Each phase may have a different magnetic order

● 1 phase found to be superconducting

● KFe2Se2-z

● K2Fe4Se5

● Two structures of KFe2Se2

(different charge orderings)

● And Others

FeSe KFe2Se

2

KxFe

2-ySe

2: Crystal Growth

● Step 1: FeSe(vapor self transport)

● Step 2: KFe2Se

2

(from melt)

● Post annealing/ quenching

● Contamination concerns

KxFe2-ySe2: Characterization

● Why is it a superconductor?

● How do the different phases interact with each other and behave independently?

Techniques:● X-Ray Diffraction

● Resistance

● Hall effect

● Magnetization

CharacterizationX-Ray diffraction:

● Crystal structure characterization

● Different crystal phases will have different characteristic peaks

Resistivity:

● CDW

● Varies greatly with stoichiometry

CharacterizationHall Effect

● Charge carrier

● FeSe has been found to have a change in the sign of the hall effect

Magnetization

● Hc1, Hc2, magnetic susceptibility

Conclusion

KxFe

2-ySe

2

● Behavior of each phase individually

● Interaction between the different phases

In General● Why high temperature

superconductors form

● Further investigate the fundamental relationship between magnetization and superconductivity

References● 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 Fong-

Chi 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 Qi-

Kun Xue. Kfe(2)se(2) is the parent compound of k-doped iron selenide superconductors. Physical Review Letters, 109, 2012.

Acknowledgments

● Petra Husanikova● Christopher Brown● Joey Lambert● Erica Smith

Sample carrier design

● Needs to fit down the central shaft of dewar

● Space considerations

● Thermal considerations

● Vacuum considerations

● Electrical contacts

– Sensors

– Utility● Replaceable parts

Sample carrier design

● Still a work in progress

● Temperature sensor

● Heating

● Electrical leads

Crystal Growth and Measurements done

(although, not related to KxFe2-xSe2)● CuxTiSe2

● Iodine vapor transport

● Grown on Temple's campus(same place we will grow KxFe2-xSe2)

Measurements:● Resistance vs.

temperature

Temperature (K)

Res

ista

nce

mea

sur e

d