[ ] [Image] [ ] Volume: Page/Article: ------------------------------------------------------------------------ Article Collection: View Collection Help (Click on the [Check Box] to add an article.) ------------------------------------------------------------------------ Phys. Rev. B 49, 17351–17359 (1994) [Issue 24 – 15 June 1994 ] [ Previous article | Next article | Issue 24 contents ] [Add to article collection] View Page Images , Figure Images or PDF (1642 kB) ------------------------------------------------------------------------ Grazing-incidence x-ray-scattering study of (001)-oriented high-quality epitaxial Co/Cr superlattices N. Metoki, W. Donner, and H. Zabel Fakultät für Physik und Astronomie, Institut für Experimentalphysik (Festkörperphysik), Ruhr-Universität Bochum, D-44780 Bochum, Federal Republic of Germany Received 18 January 1994 The structural properties of Co/Cr(001) superlattices grown by molecular-beam epitaxy have been studied by means of grazing-incidence x-ray-scattering techniques. From the in-plane diffraction pattern, we find that hcp-Co(11.0) is epitaxially grown on Cr(001) with the Co[00.1] axis parallel to Cr[110]. This epitaxial relation is equivalent to the Pitsch-Schrader orientational relationship. The Co layers exhibit a precursive structural phase transition from hcp to bcc with decreasing Co layer thickness tCo. First, the Co in-plane unit cell changes its shape from rectangular (hcp) to square (bcc), due to the epitaxial strain. Second, the intensity I of the hcp-Co\{1-bar1.1\} spots shows a continuous decrease with decreasing tCo. The intensity I is proportional to the square of the displacement delta of the Co atoms from the bcc center sites, which is the order parameter for this structural transition. This intensity decrease therefore implies that the Co lattice continuously changes its symmetry from hcp to bcc. The experimentally determined tCo dependence of delta is in good agreement with a model calculation describing the competition of the surface potential on Cr(001) and the bulk hcp potential of Co. Finally, we find that the observed anomalous out-of-plane expansion of the Co layers is a precursor of the structural transition. The non-Poisson-like behavior can be explained by a rigid-atom model which takes into account the atomic displacement during the structural transition. ©1994 The American Physical Society URL: http://link.aps.org/abstract/PRB/v49/p17351 DOI: 10.1103/PhysRevB.49.17351 PACS: 61.10.-i, 68.65.+g, 81.30.Kf ------------------------------------------------------------------------ [Add to article collection] View Page Images , Figure Images or PDF (1642 kB) [ Previous article | Next article | Issue 24 contents ] ------------------------------------------------------------------------ References (Reference links marked with [dot] may require a separate subscription.) 1. For recent reviews, see Proceedings of the International Symposium on Magnetic Ultrathin Films, Multilayers, and Surfaces, Lyon, 1992 [J. Magn. Magn. Mater. 121 (1993)]; Proceedings of the Thirty seventh Annual Conference on Magnetism and Magnetic Materials [J. Appl. Phys. 73, 10 (1993)]. 2. T. Shinjo, Surf. Sci. Rep. 12, 49 (1991) [[dot] INSPEC]. 3. S.S.P. Parkin, Phys. Rev. Lett. 67, 3598 (1991). 4. C.F. Majkrzak, J. Kwo, M. Hong, Y. Yafet, D. Gibbs, C.L. Chien and J. Bohr, Adv. Phys. 40, 99 (1991) [[dot] INSPEC]. 5. W.A.A. Macedo and W. Keune, Phys. Rev. Lett. 61, 475 (1988); W.A.A. Macedo, W. Keune and E.D. Ellerbrock, J. Magn. Magn. Mater. 93, 552 (1991) [[dot] INSPEC]. 6. B. Heinrich, Z. Celinski, J.F. Cochran, A.S. Arrott, K. Myrte and S.T. Purcell, Phys. Rev. B 47, 5077 (1993). 7. M.D. Wieczorek, D.J. Keavney, D.F. Storm and J.C. Walker, J. Magn. Magn. Mater. 121, 34 (1993), and references cited therein [[dot] INSPEC]. 8. M. Maurer, J.C. Ousset, M.F. Ravet and M. Piecuch, Mat. Res. Soc. Symp. Proc. 87, 231 (1990). 9. For example, S.M. Shapiro and S.C. Moss, Phys. Rev. B 15, 2726 (1977); F. Frey, W. Prandl, J. Schneider, C. Zeyen and K. Ziebeck, J. Phys. F 9, 603 (1979). 10. G.A. Prinz, Phys. Rev. Lett. 54, 1051 (1985); P.C. Riedi, T. Dumelow, M. Rubinstein, G.A. Prinz and S.B. Qadri, Phys. Rev. B 36, 4595 (1987); Y.U. Ydzerda, W.T. Elam, B.T. Jonker and G.A. Prinz, Phys. Rev. Lett. 62, 2480 (1989). 11. R. Walmsley, J. Thompson, D. Friedman, R.M. White and T.H. Geballe, IEEE Trans. Magn. Magn. 19, 1992 (1983). 12. N. Sato, J. Appl. Phys. 61, 1979 (1987) [[dot] SPIN][[dot] INSPEC]. 13. M.B. Stearns, C.H. Lee and T.L. Groy, Phys. Rev. B 40, 8256 (1989). 14. P. Boher, F. Giron, Ph. Houdy, P. Beauvillain, C. Chappert and P. Veillet, J. Appl. Phys. 70, 5507 (1991) [[dot] INSPEC]. 15. W. Vavra, D. Barlett, S. Elagoz, C. Uher and R. Clarke, Phys. Rev. B 47, 5500 (1993); Y. Henry, C. Mény, A. Dinia and P. Panissod, , 15037 (1993). 16. F. Scheurer, B. Carrière, J.P. Deville and E. Beaurepaire, Surf. Sci. 245, L175 (1991) [[dot] INSPEC]. 17. F. Scheurer, P. Ohresser, B. Carrière, J.P. Deville, R. Baudoing Savois and Y. Gauthier, Surf. Sci. 298, 107 (1993) [[dot] INSPEC]. 18. J. Unguris, R.J. Celotta and D.T. Pierce, Phys. Rev. Lett. 67, 140 (1991); and, 69, 1125 (1992); S.T. Purcell, W. Folkerts, M.T. Johnson, N.W.E. McGee, K. Jager, J. aan de Stegge, W.B. Zeper, W. Hoving and P. Grünberg, Phys. Rev. Lett.ibid. 67, 903 (1991). 19. F. Herman, P. Lambin and O. Jepsen, Phys. Rev. B 31, 4394 (1985); H. Hasegawa and F. Herman, 38, 4863 (1988); H. Hasegawa, 43, 10803 (1991); D. Stoeffler and F. Gautier, 44, 10389 (1991); and, Surf. Sci. 251/252, 31 (1991). 20. W. Donner, N. Metoki, A. Abromeit and H. Zabel, Phys. Rev. B 48, 14745 (1993). 21. N. Metoki, W. Donner, Th. Zeidler and H. Zabel, J. Magn. Magn. Mater. 126, 397 (1993) [[dot] INSPEC]; W. Donner, Th. Zeidler, F. Schreiber, N. Metoki and H. Zabel, J. Appl. Phys. 75, 8 (1994). 22. R. Feidenhans'l, Surf. Sci. Rep. 10, 105 (1989) [[dot] INSPEC]; Surface X Ray and Neutron Scattering, edited by H. Zabel and I.K. Robinson (Springer Verlag, Berlin, 1992), p. 181ff. 23. X. Wyckoff, Crystal Structures, 2nd ed. (John Wiley & Sons, New York, 1963), Vol. 1, p. 12. 24. W. Pitsch and A. Schrader, Arch. Eisenhütt Wes. 29, 715 (1958). 25. L.A. Bruce and H. Jaeger, Philos. Mag. A 40, 97 (1979) [[dot] INSPEC]. 26. J. Daval and D. Randet, IEEE Trans. Mag. 6, 768 (1970). 27. This expression is derived by the theoretical calculation for surface scattering geometry with distorted wave approximation [See, for example, H. Dosch, Phys. Rev. B 35, 2137 (1987)]. Note that in the present case Lambda /dis very large ( Lambda /d cong 400). 28. In the calculation for an ideal case a was chosen so as to get I =frac 14 at tCo=a. 29. American Institute of Physics Handbook, 2nd ed. (McGraw Hill, New York, 1963). 30. We changed slightly the lattice constants of Co and Co atomic radius from the known value so as to give a correct out of plane d spacing for bcc (hcp) at delta =0(1). 31. A.F. Jankowski, J. Appl. Phys. 71, 1782 (1992) [[dot] INSPEC]; and,, 3816 (1992) [[dot] INSPEC]; N. Nakayama, L. Wu, H. Dohnomae, T. Shinjo, J. Kim, and C.M. Falco, J. Magn. Magn. Mater. (to be published). 32. Y. Ohishi et al., in Multilayers, edited by M. Doyama et al., MRS Symposia Proceedings No. 10 (Materials Research Society, Pittsburgh, PA, 1989), p. 569; E.E. Fullerton, I.K. Schuller, H. Vanderstraeten and Y. Bruynseraede, Phys. Rev. B 45, 9292 (1992). 33. A. Fartash, M. Grimsditch, E.F. Fullerton and I.K. Schuller, Phys. Rev. B 47, 12813 (1993). 34. P. Sonntag, W. Donner, N. Metoki and H. Zabel, Phys. Rev. B 49, 2869 (1994). 35. P. Bödeker, A. Abromeit, K. Bröhl, P. Sonntag, N. Metoki and H. Zabel, Phys. Rev. B 47, 2353 (1993). 36. Ch. Morawe, A. Abromeit, N. Metoki, P. Sonntag, and H. Zabel, J. Mater. Res. 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