1. The swift heavy ion modification of Fe/Cr multilayer properties Małgorzata Kąc The Henryk Niewodniczański Insitute of Nuclear Physics, Polish Academy of Sciences Kraków, 6 February 2007

2. Motivation GMR read-head

3. The home-built ultrahigh-vacuum system for preparation and analysis of ultrathin films and multilayers The Henryk Niewodniczański Insitute of Nuclear Physics, Polish Academy of Sciences

4. Structural, magnetic and magnetotransport properties of Fe/Cr multilayers H M H M Magnetization Magnetoresistivity GMR CEMS Conversion Electron Mössbauer Spectroscopy R [Ω] B [T] Si (100) Fe Cr 163 MeV Au ions Number of counts Velocity [mm/s]

5. First and second configuration shell of Fe atom in bcc structure B hf (n 1,n 2 ) = B hf (0,0) – c 1 n 1 – c 2 n 2 B hf – hyperfine magnetic field

6. Fe film sandwiched between Cr films B hf [T] fraction [%] B hf [T] fraction [%] 6 ML Fe 57 Cr model number of counts [10 7 ] velocity [mm/s] real

7. number of counts B hf [T] component fraction [%] velocity [mm/s] upper 20 repetitions of Fe/Cr Interface structure in [Fe/Cr] 20 multilayers before irradiation swift heavy ions - chance to smooth the interfaces

8. as deposited 1.5 x 10 12 ions/cm 2 5 x 10 12 ions/cm 2 8 x 10 11 ions/cm 2 B hf [T] velocity [mm/s] number of counts component fraction [%] Interface structure in [Fe/Cr] 20 multilayers after irradiation after irradiation the interfaces become rougher After 163 MeV Au irradiation with fluence:

9. Irradiation influence on the antiferromagnetic coupling increase of interface roughness resulted in decrease of antiferromagnetic coupling

10. Irradiation influence on the magnetoresistance effect increase of interface roughness resulted in decay of GMR effect  R/R

11. Conclusions in Fe/Cr multilayers irradiated with swift Au ions the demixing of Fe and Cr atoms at the interfaces was not observed the increase of Au-ion fluence causes an increase of interface roughness, as evidenced by CEMS antiferromagnetic exchange coupling fraction and GMR effect decreased substantially with increasing irradiation fluence this experiment shows that increase of interface roughness in multilayer systems reduce the GMR Solutions: irradiation with other kind of ions using other way of interface modification

12. Co/Cu multilayers with surfactants Future: Fe/Cr multilayers with surfactants Marta Marszałek Robert Kruk Valeriy Tokman Stanisław Maranda Aleksander Polit Yevhen Zabila Marcel Toulemonde (Caen) Jacques Teillet (Rouen) Jean Juraszek (Rouen) Acknowledgements: