Abstract

When cobalt thin films are illuminated with femtosecond laser pulses, we observe the emission of terahertz pulses. For a cobalt film thickness less than about 40 nm, the THz electric field direction rotates when the sample is rotated about the surface normal. This azimuthal angle-dependent emission is consistent with the assumption that laser-induced changes in an in-plane magnetization are responsible for the emission. For thicker layers, however, we observe the development of an azimuthal angle-independent contribution to the THz emission which we attribute to laser-induced changes in an out-of-plane magnetization component. We show that the relative contribution of this component grows when the cobalt film thickness increases. Our observations are supported by magnetic force microscopy measurements which show that for film thicknesses below 40 nm, the magnetization is predominantly in-plane whereas for thicknesses larger than 40 nm, an out-of-plane magnetization component develops.

© 2015 Optical Society of America

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References

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  1. K. Sakai, Terahertz Optoelectronics (Springer, 2005).
    [Crossref]
  2. G. K. P. Ramanandan, G. Ramakrishnan, N. Kumar, A. J. L. Adam, and P. C. M. Planken, “Emission of terahertz pulses from nanostructured metal surfaces,” J. Phys. D: Appl. Phys. 47, 374003 (2014).
    [Crossref]
  3. F. Kadlec, P. Kuel, and J.-L. Coutaz, “Optical rectification at metal surfaces,” Opt. Lett. 29(22), 2674–2676 (2004).
    [Crossref] [PubMed]
  4. G. H. Welsh and K. Wynne, “Generation of ultrafast terahertz radiation pulses on metallic nanostructured surfaces,” Opt. Express 17(4), 2470–2480 (2009).
    [Crossref] [PubMed]
  5. G. Ramakrishnan and P. C. M. Planken, “Percolation-enhanced generation of terahertz pulses by optical rectification on ultrathin gold films,” Opt. Lett. 36(13), 2572–2574 (2011).
    [Crossref] [PubMed]
  6. E. Beaurepaire, G. M. Turner, S. M. Harrel, M. C. Beard, J.-Y. Bigot, and C. A. Schmuttenmaer, “Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses,” Appl. Phys. Lett. 84, 3465 (2004).
    [Crossref]
  7. D. J. Hilton, R. D. Averitt, C. A. Meserole, G. L. Fisher, D. J. Funk, J. D. Thompson, and A. J. Taylor, “Terahertz emission via ultrashort-pulse excitation of magnetic metal films,” Opt. Lett. 29(15), 1805–1807 (2004).
    [Crossref] [PubMed]
  8. J. Shen, X. Fan, Z. Chen, M. F. DeCamp, H. Zhang, and J. Q. Xiao, “Damping modulated terahertz emission of ferromagnetic films excited by ultrafast laser pulses,” Appl. Phys. Lett. 101, 072401 (2012).
    [Crossref]
  9. M. Battiato, K Carva, and P. M. Oppeneer, “Superdiffusive spin transport as a mechanism of ultrafast demagnetization,” Phys. Rev. Lett. 105, 027203 (2010).
    [Crossref] [PubMed]
  10. A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
    [Crossref] [PubMed]
  11. A. J. Schellekens, W. Verhoeven, T. N. Vader, and B. Koopmans, “Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films,” App. Phys. Lett. 102, 252408 (2013).
    [Crossref]
  12. Y. Martin and H. K. Wickramasinghe, “Magnetic imaging by force microscopy with 1000 A° resolution,” Appl. Phys. Lett. 50, 1455 (1987).
    [Crossref]
  13. C. T. Hsieh, J. Q. Liu, and J. T. Lue, “Magnetic force microscopy studies of domain walls in nickel and cobalt films,” Appl. Surf. Sci. 252, 1899–1909 (2005)
    [Crossref]
  14. M. Hehn, S. Padovani, K. Ounadjela, and J. P. Bucher, “Nanoscale magnetic domain structures in epitaxial cobalt films,” Phys. Rev. B 54(5), 3428–3433 (1996).
    [Crossref]
  15. J. Brandenburg, R. Huhne, L. Schultz, and V. Neu, “Domain structure of epitaxial Co films with perpendicular anisotropy,” Phys. Rev. B 79, 054429 (2009).
    [Crossref]
  16. N. Saito, H. Fujiwara, and Y. Sugita, “A new type of magnetic domain structure in negative magnetostriction Ni-Fe films,” J. Phys. Soc. Jpn. 19(7), 1116 (1964).
    [Crossref]

2014 (1)

G. K. P. Ramanandan, G. Ramakrishnan, N. Kumar, A. J. L. Adam, and P. C. M. Planken, “Emission of terahertz pulses from nanostructured metal surfaces,” J. Phys. D: Appl. Phys. 47, 374003 (2014).
[Crossref]

2013 (2)

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

A. J. Schellekens, W. Verhoeven, T. N. Vader, and B. Koopmans, “Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films,” App. Phys. Lett. 102, 252408 (2013).
[Crossref]

2012 (1)

J. Shen, X. Fan, Z. Chen, M. F. DeCamp, H. Zhang, and J. Q. Xiao, “Damping modulated terahertz emission of ferromagnetic films excited by ultrafast laser pulses,” Appl. Phys. Lett. 101, 072401 (2012).
[Crossref]

2011 (1)

2010 (1)

M. Battiato, K Carva, and P. M. Oppeneer, “Superdiffusive spin transport as a mechanism of ultrafast demagnetization,” Phys. Rev. Lett. 105, 027203 (2010).
[Crossref] [PubMed]

2009 (2)

J. Brandenburg, R. Huhne, L. Schultz, and V. Neu, “Domain structure of epitaxial Co films with perpendicular anisotropy,” Phys. Rev. B 79, 054429 (2009).
[Crossref]

G. H. Welsh and K. Wynne, “Generation of ultrafast terahertz radiation pulses on metallic nanostructured surfaces,” Opt. Express 17(4), 2470–2480 (2009).
[Crossref] [PubMed]

2005 (1)

C. T. Hsieh, J. Q. Liu, and J. T. Lue, “Magnetic force microscopy studies of domain walls in nickel and cobalt films,” Appl. Surf. Sci. 252, 1899–1909 (2005)
[Crossref]

2004 (3)

1996 (1)

M. Hehn, S. Padovani, K. Ounadjela, and J. P. Bucher, “Nanoscale magnetic domain structures in epitaxial cobalt films,” Phys. Rev. B 54(5), 3428–3433 (1996).
[Crossref]

1987 (1)

Y. Martin and H. K. Wickramasinghe, “Magnetic imaging by force microscopy with 1000 A° resolution,” Appl. Phys. Lett. 50, 1455 (1987).
[Crossref]

1964 (1)

N. Saito, H. Fujiwara, and Y. Sugita, “A new type of magnetic domain structure in negative magnetostriction Ni-Fe films,” J. Phys. Soc. Jpn. 19(7), 1116 (1964).
[Crossref]

Adam, A. J. L.

G. K. P. Ramanandan, G. Ramakrishnan, N. Kumar, A. J. L. Adam, and P. C. M. Planken, “Emission of terahertz pulses from nanostructured metal surfaces,” J. Phys. D: Appl. Phys. 47, 374003 (2014).
[Crossref]

Averitt, R. D.

Battiato, M.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

M. Battiato, K Carva, and P. M. Oppeneer, “Superdiffusive spin transport as a mechanism of ultrafast demagnetization,” Phys. Rev. Lett. 105, 027203 (2010).
[Crossref] [PubMed]

Beard, M. C.

E. Beaurepaire, G. M. Turner, S. M. Harrel, M. C. Beard, J.-Y. Bigot, and C. A. Schmuttenmaer, “Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses,” Appl. Phys. Lett. 84, 3465 (2004).
[Crossref]

Beaurepaire, E.

E. Beaurepaire, G. M. Turner, S. M. Harrel, M. C. Beard, J.-Y. Bigot, and C. A. Schmuttenmaer, “Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses,” Appl. Phys. Lett. 84, 3465 (2004).
[Crossref]

Bigot, J.-Y.

E. Beaurepaire, G. M. Turner, S. M. Harrel, M. C. Beard, J.-Y. Bigot, and C. A. Schmuttenmaer, “Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses,” Appl. Phys. Lett. 84, 3465 (2004).
[Crossref]

Brandenburg, J.

J. Brandenburg, R. Huhne, L. Schultz, and V. Neu, “Domain structure of epitaxial Co films with perpendicular anisotropy,” Phys. Rev. B 79, 054429 (2009).
[Crossref]

Bucher, J. P.

M. Hehn, S. Padovani, K. Ounadjela, and J. P. Bucher, “Nanoscale magnetic domain structures in epitaxial cobalt films,” Phys. Rev. B 54(5), 3428–3433 (1996).
[Crossref]

Carva, K

M. Battiato, K Carva, and P. M. Oppeneer, “Superdiffusive spin transport as a mechanism of ultrafast demagnetization,” Phys. Rev. Lett. 105, 027203 (2010).
[Crossref] [PubMed]

Chen, Z.

J. Shen, X. Fan, Z. Chen, M. F. DeCamp, H. Zhang, and J. Q. Xiao, “Damping modulated terahertz emission of ferromagnetic films excited by ultrafast laser pulses,” Appl. Phys. Lett. 101, 072401 (2012).
[Crossref]

Coutaz, J.-L.

DeCamp, M. F.

J. Shen, X. Fan, Z. Chen, M. F. DeCamp, H. Zhang, and J. Q. Xiao, “Damping modulated terahertz emission of ferromagnetic films excited by ultrafast laser pulses,” Appl. Phys. Lett. 101, 072401 (2012).
[Crossref]

Eschenlohr, A.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

Fan, X.

J. Shen, X. Fan, Z. Chen, M. F. DeCamp, H. Zhang, and J. Q. Xiao, “Damping modulated terahertz emission of ferromagnetic films excited by ultrafast laser pulses,” Appl. Phys. Lett. 101, 072401 (2012).
[Crossref]

Fhlisch, A.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

Fisher, G. L.

Fujiwara, H.

N. Saito, H. Fujiwara, and Y. Sugita, “A new type of magnetic domain structure in negative magnetostriction Ni-Fe films,” J. Phys. Soc. Jpn. 19(7), 1116 (1964).
[Crossref]

Funk, D. J.

Harrel, S. M.

E. Beaurepaire, G. M. Turner, S. M. Harrel, M. C. Beard, J.-Y. Bigot, and C. A. Schmuttenmaer, “Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses,” Appl. Phys. Lett. 84, 3465 (2004).
[Crossref]

Hehn, M.

M. Hehn, S. Padovani, K. Ounadjela, and J. P. Bucher, “Nanoscale magnetic domain structures in epitaxial cobalt films,” Phys. Rev. B 54(5), 3428–3433 (1996).
[Crossref]

Hilton, D. J.

Holldack, K.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

Hsieh, C. T.

C. T. Hsieh, J. Q. Liu, and J. T. Lue, “Magnetic force microscopy studies of domain walls in nickel and cobalt films,” Appl. Surf. Sci. 252, 1899–1909 (2005)
[Crossref]

Huhne, R.

J. Brandenburg, R. Huhne, L. Schultz, and V. Neu, “Domain structure of epitaxial Co films with perpendicular anisotropy,” Phys. Rev. B 79, 054429 (2009).
[Crossref]

Kachel, T.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

Kadlec, F.

Koopmans, B.

A. J. Schellekens, W. Verhoeven, T. N. Vader, and B. Koopmans, “Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films,” App. Phys. Lett. 102, 252408 (2013).
[Crossref]

Kuel, P.

Kumar, N.

G. K. P. Ramanandan, G. Ramakrishnan, N. Kumar, A. J. L. Adam, and P. C. M. Planken, “Emission of terahertz pulses from nanostructured metal surfaces,” J. Phys. D: Appl. Phys. 47, 374003 (2014).
[Crossref]

Liu, J. Q.

C. T. Hsieh, J. Q. Liu, and J. T. Lue, “Magnetic force microscopy studies of domain walls in nickel and cobalt films,” Appl. Surf. Sci. 252, 1899–1909 (2005)
[Crossref]

Lue, J. T.

C. T. Hsieh, J. Q. Liu, and J. T. Lue, “Magnetic force microscopy studies of domain walls in nickel and cobalt films,” Appl. Surf. Sci. 252, 1899–1909 (2005)
[Crossref]

Maldonado, P.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

Martin, Y.

Y. Martin and H. K. Wickramasinghe, “Magnetic imaging by force microscopy with 1000 A° resolution,” Appl. Phys. Lett. 50, 1455 (1987).
[Crossref]

Meserole, C. A.

Mitzner, R.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

Neu, V.

J. Brandenburg, R. Huhne, L. Schultz, and V. Neu, “Domain structure of epitaxial Co films with perpendicular anisotropy,” Phys. Rev. B 79, 054429 (2009).
[Crossref]

Oppeneer, P. M.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

M. Battiato, K Carva, and P. M. Oppeneer, “Superdiffusive spin transport as a mechanism of ultrafast demagnetization,” Phys. Rev. Lett. 105, 027203 (2010).
[Crossref] [PubMed]

Ounadjela, K.

M. Hehn, S. Padovani, K. Ounadjela, and J. P. Bucher, “Nanoscale magnetic domain structures in epitaxial cobalt films,” Phys. Rev. B 54(5), 3428–3433 (1996).
[Crossref]

Padovani, S.

M. Hehn, S. Padovani, K. Ounadjela, and J. P. Bucher, “Nanoscale magnetic domain structures in epitaxial cobalt films,” Phys. Rev. B 54(5), 3428–3433 (1996).
[Crossref]

Planken, P. C. M.

G. K. P. Ramanandan, G. Ramakrishnan, N. Kumar, A. J. L. Adam, and P. C. M. Planken, “Emission of terahertz pulses from nanostructured metal surfaces,” J. Phys. D: Appl. Phys. 47, 374003 (2014).
[Crossref]

G. Ramakrishnan and P. C. M. Planken, “Percolation-enhanced generation of terahertz pulses by optical rectification on ultrathin gold films,” Opt. Lett. 36(13), 2572–2574 (2011).
[Crossref] [PubMed]

Pontius, N.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

Ramakrishnan, G.

G. K. P. Ramanandan, G. Ramakrishnan, N. Kumar, A. J. L. Adam, and P. C. M. Planken, “Emission of terahertz pulses from nanostructured metal surfaces,” J. Phys. D: Appl. Phys. 47, 374003 (2014).
[Crossref]

G. Ramakrishnan and P. C. M. Planken, “Percolation-enhanced generation of terahertz pulses by optical rectification on ultrathin gold films,” Opt. Lett. 36(13), 2572–2574 (2011).
[Crossref] [PubMed]

Ramanandan, G. K. P.

G. K. P. Ramanandan, G. Ramakrishnan, N. Kumar, A. J. L. Adam, and P. C. M. Planken, “Emission of terahertz pulses from nanostructured metal surfaces,” J. Phys. D: Appl. Phys. 47, 374003 (2014).
[Crossref]

Saito, N.

N. Saito, H. Fujiwara, and Y. Sugita, “A new type of magnetic domain structure in negative magnetostriction Ni-Fe films,” J. Phys. Soc. Jpn. 19(7), 1116 (1964).
[Crossref]

Sakai, K.

K. Sakai, Terahertz Optoelectronics (Springer, 2005).
[Crossref]

Schellekens, A. J.

A. J. Schellekens, W. Verhoeven, T. N. Vader, and B. Koopmans, “Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films,” App. Phys. Lett. 102, 252408 (2013).
[Crossref]

Schmuttenmaer, C. A.

E. Beaurepaire, G. M. Turner, S. M. Harrel, M. C. Beard, J.-Y. Bigot, and C. A. Schmuttenmaer, “Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses,” Appl. Phys. Lett. 84, 3465 (2004).
[Crossref]

Schultz, L.

J. Brandenburg, R. Huhne, L. Schultz, and V. Neu, “Domain structure of epitaxial Co films with perpendicular anisotropy,” Phys. Rev. B 79, 054429 (2009).
[Crossref]

Shen, J.

J. Shen, X. Fan, Z. Chen, M. F. DeCamp, H. Zhang, and J. Q. Xiao, “Damping modulated terahertz emission of ferromagnetic films excited by ultrafast laser pulses,” Appl. Phys. Lett. 101, 072401 (2012).
[Crossref]

Stamm, C.

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

Sugita, Y.

N. Saito, H. Fujiwara, and Y. Sugita, “A new type of magnetic domain structure in negative magnetostriction Ni-Fe films,” J. Phys. Soc. Jpn. 19(7), 1116 (1964).
[Crossref]

Taylor, A. J.

Thompson, J. D.

Turner, G. M.

E. Beaurepaire, G. M. Turner, S. M. Harrel, M. C. Beard, J.-Y. Bigot, and C. A. Schmuttenmaer, “Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses,” Appl. Phys. Lett. 84, 3465 (2004).
[Crossref]

Vader, T. N.

A. J. Schellekens, W. Verhoeven, T. N. Vader, and B. Koopmans, “Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films,” App. Phys. Lett. 102, 252408 (2013).
[Crossref]

Verhoeven, W.

A. J. Schellekens, W. Verhoeven, T. N. Vader, and B. Koopmans, “Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films,” App. Phys. Lett. 102, 252408 (2013).
[Crossref]

Welsh, G. H.

Wickramasinghe, H. K.

Y. Martin and H. K. Wickramasinghe, “Magnetic imaging by force microscopy with 1000 A° resolution,” Appl. Phys. Lett. 50, 1455 (1987).
[Crossref]

Wynne, K.

Xiao, J. Q.

J. Shen, X. Fan, Z. Chen, M. F. DeCamp, H. Zhang, and J. Q. Xiao, “Damping modulated terahertz emission of ferromagnetic films excited by ultrafast laser pulses,” Appl. Phys. Lett. 101, 072401 (2012).
[Crossref]

Zhang, H.

J. Shen, X. Fan, Z. Chen, M. F. DeCamp, H. Zhang, and J. Q. Xiao, “Damping modulated terahertz emission of ferromagnetic films excited by ultrafast laser pulses,” Appl. Phys. Lett. 101, 072401 (2012).
[Crossref]

App. Phys. Lett. (1)

A. J. Schellekens, W. Verhoeven, T. N. Vader, and B. Koopmans, “Investigating the contribution of superdiffusive transport to ultrafast demagnetization of ferromagnetic thin films,” App. Phys. Lett. 102, 252408 (2013).
[Crossref]

Appl. Phys. Lett. (3)

Y. Martin and H. K. Wickramasinghe, “Magnetic imaging by force microscopy with 1000 A° resolution,” Appl. Phys. Lett. 50, 1455 (1987).
[Crossref]

E. Beaurepaire, G. M. Turner, S. M. Harrel, M. C. Beard, J.-Y. Bigot, and C. A. Schmuttenmaer, “Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses,” Appl. Phys. Lett. 84, 3465 (2004).
[Crossref]

J. Shen, X. Fan, Z. Chen, M. F. DeCamp, H. Zhang, and J. Q. Xiao, “Damping modulated terahertz emission of ferromagnetic films excited by ultrafast laser pulses,” Appl. Phys. Lett. 101, 072401 (2012).
[Crossref]

Appl. Surf. Sci. (1)

C. T. Hsieh, J. Q. Liu, and J. T. Lue, “Magnetic force microscopy studies of domain walls in nickel and cobalt films,” Appl. Surf. Sci. 252, 1899–1909 (2005)
[Crossref]

J. Phys. D: Appl. Phys. (1)

G. K. P. Ramanandan, G. Ramakrishnan, N. Kumar, A. J. L. Adam, and P. C. M. Planken, “Emission of terahertz pulses from nanostructured metal surfaces,” J. Phys. D: Appl. Phys. 47, 374003 (2014).
[Crossref]

J. Phys. Soc. Jpn. (1)

N. Saito, H. Fujiwara, and Y. Sugita, “A new type of magnetic domain structure in negative magnetostriction Ni-Fe films,” J. Phys. Soc. Jpn. 19(7), 1116 (1964).
[Crossref]

Nat. Mater. (1)

A. Eschenlohr, M. Battiato, P. Maldonado, N. Pontius, T. Kachel, K. Holldack, R. Mitzner, A. Fhlisch, P. M. Oppeneer, and C. Stamm, “Ultrafast spin transport as key to femtosecond demagnetization,” Nat. Mater. 12, 332–336 (2013).
[Crossref] [PubMed]

Opt. Express (1)

Opt. Lett. (3)

Phys. Rev. B (2)

M. Hehn, S. Padovani, K. Ounadjela, and J. P. Bucher, “Nanoscale magnetic domain structures in epitaxial cobalt films,” Phys. Rev. B 54(5), 3428–3433 (1996).
[Crossref]

J. Brandenburg, R. Huhne, L. Schultz, and V. Neu, “Domain structure of epitaxial Co films with perpendicular anisotropy,” Phys. Rev. B 79, 054429 (2009).
[Crossref]

Phys. Rev. Lett. (1)

M. Battiato, K Carva, and P. M. Oppeneer, “Superdiffusive spin transport as a mechanism of ultrafast demagnetization,” Phys. Rev. Lett. 105, 027203 (2010).
[Crossref] [PubMed]

Other (1)

K. Sakai, Terahertz Optoelectronics (Springer, 2005).
[Crossref]

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Figures (10)

Fig. 1
Fig. 1 XRD measurement of a 100 nm thick cobalt film deposited on the glass substrate.
Fig. 2
Fig. 2 Experimental setup for the generation and detection of THz pulses. The pump beam is incident on the sample at (a) a 45° degree angle of incidence and (b) a 0° angle of incidence. In (b), the THz emission is detected in the back-reflected direction.
Fig. 3
Fig. 3 (a) Measured THz electric field vs. time, emitted from a 100 nm thick cobalt film deposited on the glass substrate at 45° angle of incidence (b) Pump power dependence of THz emission from cobalt thin films. (c) The measured percentage of absorbed pump power (blue) and the electric field amplitude of the THz pulses emitted (red) from the cobalt thin films, as a function of pump beam polarization.
Fig. 4
Fig. 4 (a) Schematic detail of setup used to apply an external magnetic field to cobalt thin films. (b) Measured THz emission from a 40 nm thick Co film on glass, as a function of time. Black and red traces indicate THz emission with magnetic fields applied in opposite directions.
Fig. 5
Fig. 5 The azimuthal angle dependence of the measured THz electric-field amplitude emitted by a (a) 40 nm (b) 60 nm (c) 80 nm (d) 125 nm (e) 150 nm and (f) 250 nm thick cobalt film. Incident light is p-polarized. Error bars indicate the RMS uncertainty in the measured THz amplitude.
Fig. 6
Fig. 6 Measured p-polarized and s-polarized component of the emitted THz pulse for 30 nm thick cobalt film. Error bars indicate the RMS uncertainty in the measured THz amplitude.
Fig. 7
Fig. 7 Measured p-polarized THz emission from 40 nm (black) and 250 nm (red) thick cobalt films at a 0° angle of incidence.
Fig. 8
Fig. 8 (a) Percentage reflection, transmission and absorption of the pump laser pulses by different thicknesses of cobalt thin films. (b) p-polarized THz emission as a function of thickness of cobalt film deposited on the glass substrate.
Fig. 9
Fig. 9 Magnetic force microscope images of cobalt thin films on glass with different thicknesses. No domains are observed for thin cobalt films; domains start appearing when the thickness of the film crosses the critical thickness (40 nm). For thicker cobalt films, the width of the domains increases as we increase the thickness of the film.
Fig. 10
Fig. 10 Schematic overview of our results. (a) THz generation from thin cobalt films at a 45° angle of incidence (b) THz generation from thin cobalt films at a 0° angle of incidence (c) THz generation from thick cobalt films at a 45° angle of incidence (d) Absence of THz emission from thick cobalt films at a 0° angle of incidence. Incident light is p-polarized

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