Accessing the fundamentals of magnetotransport in metals with terahertz probes


Spin-dependent conduction in metals underlies all modern magnetic memory technologies, such as giant magnetoresistance (GMR). The charge current in ferromagnetic transition metals is carried by two non-mixing populations of sp-band Fermi-level electrons: one of majority-spin and one of minority-spin. These electrons experience spin-dependent momentum scattering with localized electrons, which originate from the spin-split d-band. The direct observation of magnetotransport under such fundamental conditions, however, requires magnetotransport measurements on the same timescale as the electron momentum scattering, which takes place in the sub-100 fs regime. Using terahertz electromagnetic probes, we directly observe the magnetotransport in a metallic system under the fundamental conditions, and determine the spin-dependent densities and momentum scattering times of conduction electrons. We show that traditional measurements significantly underestimate the spin asymmetry in electron scattering, a key parameter responsible for effects such as GMR. Furthermore, we demonstrate the possibility of magnetic modulation of terahertz waves, along with heat- and contact-free GMR readout using ultrafast terahertz signals.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Illustration of spin-dependent conduction in a spin valve, and the sample structure.
Figure 2: Terahertz magnetospectroscopy experiment.
Figure 3: Results of terahertz magnetospectroscopy revealing the fundamental parameters of magnetotransport.


  1. 1

    McFadyen, I. R., Fullerton, E. E. & Carey, M. J. State-of-the-art magnetic hard disk drives. MRS Bull. 31, 379–383 (2006).

    Article  Google Scholar 

  2. 2

    Baibich, M. N. et al. Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. Phys. Rev. Lett. 61, 2472–2475 (1988).

    ADS  Article  Google Scholar 

  3. 3

    Grünberg, P., Schreiber, R., Pang, Y., Brodsky, M. B. & Sowers, H. Layered magnetic structures: Evidence for antiferromagnetic coupling of Fe layers across Cr interlayers. Phys. Rev. Lett. 57, 2442–2445 (1986).

    ADS  Article  Google Scholar 

  4. 4

    Binasch, G., Grünberg, P., Saurenbach, F. & Zinn, W. Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange. Phys. Rev. B 39, 4828–4830 (1989).

    ADS  Article  Google Scholar 

  5. 5

    Hirota, E., Sakakima, H. & Inomata, K. Giant Magneto-Resistance Devices (Springer, 2002).

    Google Scholar 

  6. 6

    Stöhr, J. & Siegmann, H. C. Magnetism: From Fundamentals to Nanoscale Dynamics (Springer, 2006).

    Google Scholar 

  7. 7

    Mott, N. F. The electrical conductivity of transition metals. Proc. R. Soc. Lond. A 153, 699–717 (1936).

    ADS  Article  Google Scholar 

  8. 8

    Motzko, N. et al. Spin relaxation in Cu and Al spin conduits. Phys. Status Solidi A 211, 986–990 (2014).

    ADS  Article  Google Scholar 

  9. 9

    Villamor, E., Isasa, M., Hueso, L. & Casanova, F. Contribution of defects to the spin relaxation in copper nanowires. Phys. Rev. B 87, 094417 (2013).

    ADS  Article  Google Scholar 

  10. 10

    Jedema, F. J., Filip, A. T. & van Wees, B. J. Electrical spin injection and accumulation at room temperature in an all-metal mesoscopic spin valve. Nature 410, 345–348 (2001).

    ADS  Article  Google Scholar 

  11. 11

    Laman, N. & Grischkowsky, D. Terahertz conductivity of thin metal films. Appl. Phys. Lett. 93, 051105 (2008).

    ADS  Article  Google Scholar 

  12. 12

    Melnikov, A. et al. Ultrafast transport of laser-excited spin-polarized carriers in Au/Fe/MgO(001). Phys. Rev. Lett. 107, 076601 (2011).

    ADS  Article  Google Scholar 

  13. 13

    Aeschlimann, M. et al. Ultrafast spin-dependent electron dynamics in fcc Co. Phys. Rev. Lett. 79, 5158–5161 (1997).

    ADS  Article  Google Scholar 

  14. 14

    Lisowski, M. et al. Femtosecond electron and spin dynamics in Gd(0001) studied by time-resolved photoemission and magneto-optics. Phys. Rev. Lett. 95, 137402 (2005).

    ADS  Article  Google Scholar 

  15. 15

    Goris, A. et al. Role of spin-flip exchange scattering for hot-electron lifetimes in cobalt. Phys. Rev. Lett. 107, 026601 (2011).

    ADS  Article  Google Scholar 

  16. 16

    Valet, T. & Fert, A. Theory of the perpendicular magnetoresistance in magnetic multilayers. Phys. Rev. B 48, 7099–7113 (1993).

    ADS  Article  Google Scholar 

  17. 17

    Zarate, E., Apell, P. & Echenique, P. M. Calculation of low-energy-electron lifetimes. Phys. Rev. B 60, 2326–2332 (1999).

    ADS  Article  Google Scholar 

  18. 18

    Hong, J. & Mills, D. L. Spin dependence of the inelastic electron mean free path in Fe and Ni: Explicit calculations and implications. Phys. Rev. B 62, 5589–5600 (2000).

    ADS  Article  Google Scholar 

  19. 19

    Zhukov, V. P., Chulkov, E. V. & Echenique, P. M. Lifetimes and inelastic mean free path of low-energy excited electrons in Fe, Ni, Pt, and Au: Ab initio GW+T calculations. Phys. Rev. B 73, 125105 (2006).

    ADS  Article  Google Scholar 

  20. 20

    Zhukov, V. P., Chulkov, E. V. & Echenique, P. M. Lifetimes of excited electrons in Fe and Ni: First-principles GW and the T-matrix theory. Phys. Rev. Lett. 93, 096401 (2004).

    ADS  Article  Google Scholar 

  21. 21

    Beaurepaire, E., Merle, J., Daunois, A. & Bigot, J. Ultrafast spin dynamics in ferromagnetic nickel. Phys. Rev. Lett. 76, 4250–4253 (1996).

    ADS  Article  Google Scholar 

  22. 22

    Beaurepaire, E. et al. Coherent terahertz emission from ferromagnetic films excited by femtosecond laser pulses. Appl. Phys. Lett. 84, 3465–3467 (2004).

    ADS  Article  Google Scholar 

  23. 23

    Kirilyuk, A., Kimel, A. V. & Rasing, T. Ultrafast optical manipulation of magnetic order. Rev. Mod. Phys. 82, 2731–2784 (2010).

    ADS  Article  Google Scholar 

  24. 24

    Walowski, J. et al. Energy equilibration processes of electrons, magnons, and phonons at the femtosecond time scale. Phys. Rev. Lett. 101, 237401 (2008).

    ADS  Article  Google Scholar 

  25. 25

    Malinowski, G. et al. Control of speed and efficiency of ultrafast demagnetization by direct transfer of spin angular momentum. Nature Phys. 4, 855–858 (2008).

    ADS  Article  Google Scholar 

  26. 26

    Kampfrath, T. et al. Terahertz spin current pulses controlled by magnetic heterostructures. Nature Nanotechnol. 8, 256–260 (2013).

    ADS  Article  Google Scholar 

  27. 27

    Pfau, B. et al. Ultrafast optical demagnetization manipulates nanoscale spin structure in domain walls. Nature Commun. 3, 1100 (2012).

    ADS  Article  Google Scholar 

  28. 28

    Eschenlohr, A. et al. Ultrafast spin transport as key to femtosecond demagnetization. Nature Mater. 12, 332–336 (2013).

    ADS  Article  Google Scholar 

  29. 29

    Tonouchi, M. Cutting-edge terahertz technology. Nature Photon. 1, 97–105 (2007).

    ADS  Article  Google Scholar 

  30. 30

    Ulbricht, R., Hendry, E., Shan, J., Heinz, T. F. & Bonn, M. Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy. Rev. Mod. Phys. 83, 543–586 (2011).

    ADS  Article  Google Scholar 

  31. 31

    Scheffler, M., Dressel, M., Jourdan, M. & Adrian, H. Extremely slow Drude relaxation of correlated electrons. Nature 438, 1135–1137 (2005).

    ADS  Article  Google Scholar 

  32. 32

    Mics, Z., D’Angio, A., Jensen, S. A., Bonn, M. & Turchinovich, D. Density-dependent electron scattering in photoexcited GaAs in strongly diffusive regime. Appl. Phys. Lett. 102, 231120 (2013).

    ADS  Article  Google Scholar 

  33. 33

    Kampfrath, T. et al. Coherent terahertz control of antiferromagnetic spin waves. Nature Photon. 5, 31–34 (2011).

    ADS  Article  Google Scholar 

  34. 34

    Jin, Z. et al. Single-pulse terahertz coherent control of spin resonance in the canted antiferromagnet YFeO3, mediated by dielectric anisotropy. Phys. Rev. B 87, 094422 (2013).

    ADS  Article  Google Scholar 

  35. 35

    Kubacka, T. et al. Large-amplitude spin dynamics driven by a THz pulse in resonance with an electromagnon. Science 343, 1333–1336 (2014).

    ADS  Article  Google Scholar 

  36. 36

    Parkin, S. S. P. & Mauri, D. Spin engineering: Direct determination of the Ruderman–Kittel–Kasuya–Yosida far-field range function in ruthenium. Phys. Rev. B 44, 7131–7134 (1991).

    ADS  Article  Google Scholar 

  37. 37

    Hartmann, U. (ed.) Magnetic Multilayers and Giant Magnetoresistance: Fundamentals and Industrial Applications (Springer, 2000).

  38. 38

    Zahn, P., Binder, J., Mertig, I., Zeller, R. & Dederichs, P. H. Origin of giant magnetoresistance: Bulk or interface scattering. Phys. Rev. Lett. 80, 4309–4312 (1998).

    ADS  Article  Google Scholar 

  39. 39

    Dieny, B. et al. Giant magnetoresistance of magnetically soft sandwiches: Dependence on temperature and on layer thickness. Phys. Rev. B 45, 806–813 (1992).

    ADS  Article  Google Scholar 

  40. 40

    Weiss, R., Mattheis, R. & Reiss, G. Advanced giant magnetoresistance technology for measurement applications. Meas. Sci. Technol. 24, 082001 (2013).

    ADS  Article  Google Scholar 

  41. 41

    Hoffmann, M. C. & Turchinovich, D. Semiconductor saturable absorbers for ultrafast terahertz signals. Appl. Phys. Lett. 96, 151110 (2010).

    ADS  Article  Google Scholar 

  42. 42

    Turchinovich, D., Hvam, J. M. & Hoffmann, M. C. Self-phase modulation of a single-cycle terahertz pulse by nonlinear free-carrier response in a semiconductor. Phys. Rev. B 85, 201304(R) (2012).

    ADS  Article  Google Scholar 

  43. 43

    Kampfrath, T., Tanaka, K. & Nelson, K. A. Resonant and nonresonant control over matter and light by intense terahertz transients. Nature Photon. 7, 680–690 (2013).

    ADS  Article  Google Scholar 

  44. 44

    Walther, M. et al. Terahertz conductivity of thin gold films at the metal-insulator percolation transition. Phys. Rev. B 76, 125408 (2007).

    ADS  Article  Google Scholar 

  45. 45

    Smith, N. V. Classical generalization of the Drude formula for the optical conductivity. Phys. Rev. B 64, 155106 (2001).

    ADS  Article  Google Scholar 

  46. 46

    Nemec, H. et al. Charge transport in TiO films with complex percolation pathways investigated by time-resolved terahertz spectroscopy. IEEE Trans. THz Sci. Technol. 3, 302–313 (2013).

    Article  Google Scholar 

  47. 47

    Tsymbal, E. Y. & Pettifor, D. G. Perspectives of giant magnetoresistance. Solid State Phys. 56, 113–237 (2001).

    Article  Google Scholar 

  48. 48

    Ignatenko, S. A. Effect of interfacial s-d scattering on transport in structures ferromagnet/insulator/ferromagnet. Tech. Phys. 51, 1398–1404 (2006).

    Article  Google Scholar 

  49. 49

    Langlinais, J. & Callaway, J. Energy bands in ferromagnetic nickel. Phys. Rev. B 5, 124–134 (1972).

    ADS  Article  Google Scholar 

  50. 50

    Tawil, R. A. & Callaway, J. Energy bands in ferromagnetic iron. Phys. Rev. B 7, 4242–4252 (1973).

    ADS  Article  Google Scholar 

  51. 51

    Soulen, R. J. Jr et al. Measuring the spin polarization of a metal with a superconducting point contact. Science 282, 85–88 (1998).

    ADS  Article  Google Scholar 

  52. 52

    Zhang, X.-G. & Butler, W. H. Band structure, evanescent states, and transport in spin tunnel junctions. J. Phys. Condens. Matter 15, R1603–R1639 (2003).

    ADS  Article  Google Scholar 

  53. 53

    Žutić, I., Fabian, J. & Sarma, S. Spintronics: Fundamentals and applications. Rev. Mod. Phys. 76, 323–410 (2004).

    ADS  Article  Google Scholar 

Download references


We are grateful to A. Fert, G. Güntherodt and M. Jourdan for their comments on this work, and to Z. Mics, I. Ivanov and F. D’Angelo for helpful discussions and assistance. We acknowledge financial support by EU Career Integration Grant 334324 LIGHTER, Max Planck Society, Graduate School of Excellence Materials Science in Mainz (MAINZ) GSC 266, the EU (MASPIC, ERC-2007-StG 208162; WALL, FP7-PEOPLE-2013-ITN 608031), the DFG, Research Center of Innovative and Emerging Materials CINEMA, and the EFRE Project 81037755 ‘STeP’ (Spintronic Technology Platform Rhineland-Palatinate).

Author information




D.T. and M.K. conceived the project. Z.J. and D.T. performed the terahertz experiments, and A.Tkach and M.K. performed the static characterization. F.C., V.S. and H.G. produced the samples. Z.J. and D.T. analysed the terahertz data, with the help of M.B., T.K. and A.Thomas. D.T. wrote the paper with contributions from Z.J., M.K., T.K., A.Thomas and M.B. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to Dmitry Turchinovich.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 530 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Jin, Z., Tkach, A., Casper, F. et al. Accessing the fundamentals of magnetotransport in metals with terahertz probes. Nature Phys 11, 761–766 (2015).

Download citation

Further reading


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing