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Magnetism, Magnetic Materials and Structures

 
Most substance has response in a magnetic field. We study magnetic properties to explore fundamental physics mostly in magnetic materials and nanostructures.
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Spin polarization

- Half metals

- Highly spin-polarized materials

- Generation and detection of a spin-polarized current

- Manipulation of spin polarization

 
Selected publications:
Using structural disorder to enhance the magnetism and spin-polarization in FexSi1−x thin films for spintronics
J Karel, Y N Zhang, C Bordel, K H Stone, T. Y. Chen, C A Jenkins, David J Smith, J Hu, R Q Wu, S M Heald, J B Kortright and F Hellman,
Materials Research Express 1 026102 (2014).
Fabrication of highly spin-polarized Co2FeAl0.5Si0.5 thin-films
M. Vahidi, J. A. Gifford*, S. K. Zhang, S. Krishnamurthy, Z. G. Yu, L. Yu, M. Huang, C. Youngbull, T. Y. Chen, and N. Newman,
APL Materials 2, 046108 (2014).
Effect of three dimensional interface in determination of spin polarization using Andreev reflection spectroscopy
J. A. Gifford, C. N. Snider, J. Martinez, and T. Y. Chen,
J. Appl. Phys. 113, 17B105 (2013).
Unified formalism of Andreev reflection at a ferromagnet/superconductor interface
T. Y. Chen, Z. Tesanovic, and C. L. Chien
Phys. Rev. Lett., 109, 146602 (2012).
Pronounced effect of extra resistance in point contact Andreev reflection
T. Y. Chen, S. X. Huang, and C. L. Chien,
Phys. Rev. B, 81, 214444(2010).
Spin polarization of amorphous ferromagnet FeCoB determined by Andreev reflection
S. X. Huang, T. Y. Chen, and C. L. Chien,
Appl. Phys. Lett.92, 242509 (2008).
Enhanced Curie temperature and spin polarization in Mn4FeGe3
T. Y. Chen, C. L. Chien and C. Petrovic,
Appl. Phys. Lett. 91, 142505 (2007).
Composition controlled spin polarization in Co1-xFexS2 alloys
C. Leighton, M. Manno, A. Cady, J. W. Freeland, L. Wang, K. Umemoto, R. M. Wentzcovitch, T. Y. Chen, C. L. Chien, P. L. Kuhns, M. J. R. Hoch, A. P. Reyes, W. G. Moulton, E. D. Dahlberg, J. Checkelsky and J. Eckert,
J. Phys.: Condens. Matter19, 315219 (2007) (INVITED REVIEW).
Sulfur stoichiometry effects in highly spin polarized CoS2 single crystals
L. Wang, T. Y. Chen, C. L. Chien, and C. Leighton,
Appl. Phys. Lett. 88, 232509 (2006).
Composition controlled spin polarization in Co1-xFexS2: electronic, magnetic, and thermodynamic properties
L. Wang, T. Y. Chen, C. L. Chien, J. G. Checkelsky, J. C. Eckert, E. D. Dahlberg, K. Umemoto, R. M. Wentzcovitch, and C. Leighton,
Phys. Rev. B 73, 144402 (2006).
Co1-xFexS2: a tunable source of highly spin-polarized electrons
L. Wang, K. Umemoto, R.M. Wentzcovitch, T. Y. Chen, C.L. Chien, J.G. Checkelsky, J.C. Eckert, E.D. Dahlberg and C. Leighton,
Phys. Rev. Lett. 94, 056602 (2005).
Spin-dependent band structure effects and measurement of the spin polarization in the candidate half-metal CoS2
L. Wang, T. Y. Chen and C. Leighton,
Phys. Rev. B 69, 094412 (2004).
Magnetic, structural, and transport properties of the Heusler alloys Co2MnSi and NiMnSb
Lance Ritchie and Gang Xiao, Y. Ji, T. Y. Chen, C. L. Chien, Ming Zhang, Jinglan Chen, Zhuhong Liu, Guangheng Wu, and X. X. Zhang,
Phys. Rev. B 68, 104430 (2003).
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Spin accumulation


- Spin caloritronics

- Spin diffusion

- Anomalous/Spin Hall effect

- Inversed spin Hall effect

- Nernst effect

- Spin Seebeck effect

 
 

Selected publications:

Control of thermal gradient using thermoelectric coolers for study of thermal effects
J. Zhang, J. A. Gifford, G. J. Zhao, D. R. Kim, C. N. Snider, N. Vargas, and T. Y. Chen,
J. Appl. Phys. 117, 17C508 (2015).
 
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Spin torque

We study spin transfer torque effects in magnetic nanostructures.

- Point-contact spin injection

- Magnetic nanostructures

 
 

Selected publications:

Enhanced magnetoresistance induced by spin transfer torque in granular films with a magnetic field
T. Y. Chen, S. X. Huang, C. L. Chien and M. D. Stiles,
Phys. Rev. Lett.96, 207203 (2006).
Current-driven switching in a single exchange-biased ferromagnetic layer
T. Y. Chen, Y. Ji, C. L. Chien and M. D. Stiles,
J. Appl. Phys. 97, 10C709 (2005).
Current-driven switching in a single exchange-biased ferromagnetic layer
T. Y. Chen, Y. Ji, C. L. Chien and M. D. Stiles,
Phys. Rev. Lett. 93, 026601 (2004).
Switching by point-contact spin injection in a continuous film
T. Y. Chen, Y. Ji and C. L. Chien,
Appl. Phys. Lett. 84, 380 (2004).
 
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Magnetoresistive phenomena

Resistance of many materials and structures changes in an external magnetic field. This can be utilized to study fundamental science and also a lot of applications.

- Ordinary magnetoresistance (OMR)

- Anisotropic magnetoresistance (AMR)

- Giant magnetoresistance (GMR)

- Tunnel magnetoresistance (TMR)

- Collossal magnetoresistance (CMR)

 
Selected publications:
Colossal magnetoresistance of polycrystalline (La0.7Tb0.3)2/3Ca1/3MnO3 at low drive field
Wang Jing-hua, Chen Ting-yong, Wu Jian-hua, Dai Dao-sheng, Nie Jia-cai, and Chao Bai-ru,
Chinese Phys. Lett. 16, 597 (1999).
The shift of the magnetic transition temperature in perovskite oxides caused by magnetostriction
J. H. Wang, H. Y. Chen, J. H. Wu, Z. X. Liu, T. Y. Chen and D. S. Dai,
Solid State Communications, 108(9), 701 (1998).
Magnetoresistance, coercivity, and aging of [FeNi/Cu/Co/Cu] spin valve multilayers
Rui-yi Fang, Ying-lei Yu, Ting-yong Chen, and Dao-sheng Dai,
Acta Physica Sinica, 46, 1841(1997).
Study on magnetoresistance coercivity and aging for [FeNi/Cu/Co/Cu]N spin valve multilayered films
Rui-yi Fang, Ting-yong Chen, Ying-lei Yu, and Dao-sheng Dai,
J. Appl. Phys.82 (8), 3957 (1997).
Study on magnetoresistance coercivity and aging effects in for [FeNi/Cu/Co/Cu]N spin valve multilayered films
Rui-yi Fang, Ting-yong Chen, Wan Hong, and Dao-sheng Dai,
IEEE Trans. Magn. 33, 3571 (1997).
 
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Manipulation of magnetic properties

 

Selected publications:

 
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Magnetic properties

We are interested in magnetic properties detectable by these techniques:

- Viberating Sample Magnetometer (VSM)

- Superconducting QUantum Interference Device (SQUID)

- Magnetic Force Microscopy (MFM)

- Magneto Optic Kerr Effect (MOKE)

 
 

Selected publications:

 
 
 
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Other effects related to magnetism

 
 
 
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