1 Structure-related changes in magnetoresistance of Co 90 Fe 10 /Cu and Co 90 Fe 10 /Cu 85 Ag 10 Au 5 multilayers D. Rafaja Inst. of Physical Metallurgy, TU Bergakademie Freiberg J. Ebert, G. Miehe, N. Martz, M. Knapp, B. Stahl, M. Ghafari, H. Hahn and H. Fuess Inst. of Materials Science, TU Darmstadt P. Schmollengruber, P. Farber and H.Siegle Robert Bosch GmbH, Stuttgart

2 GMR multilayers Co 90 Fe 10 /(Cu,Ag,Au) Si (111) SiO 2 (750  m) Fe (4.4 nm) Co 90 Fe 10 (1.1 nm) Cu (2.2 nm) 20x Si (111) SiO 2 (750  m) Fe (4.4 nm) Co 90 Fe 10 (1.1 nm) Cu 85 Ag 10 Au 5 (2.2 nm) Co 90 Fe 10 /Cu Co 90 Fe 10 /Cu 85 Ag 10 Au 5 Soft annealing: 1 hour at °C substrate buffer

3 Magnetoresistance Co 90 Fe 10 /Cu Co 90 Fe 10 /Cu 85 Ag 10 Au 5 Co 90 Fe 10 /Cu Co 90 Fe 10 / Cu 85 Ag 10 Au 5

4 Anomalous X-ray scattering T.Bigault, F.Bocquet, S.Labat, O.Thomas and H.Renevier, Phys.Rev.B 64 (2001) Fe 27 Co 28 Ni 29 Cu 47 Ag 79 Au

5 Experimental set-up (conventional) X-ray tube CuK Göbel mirror Sample Secondary graphite monochromator Detector Slit 0.1mm Slit 0.05 mm = Å Seifert – PTS

6 Experimental set-up (HASYLAB) Mirror Sample Secondary graphite monochromator Detector Slit 0.1mm Slit 0.05 mm Beamline B2 2xGe(111) PETRA = 1.13 Å = 1.37 Å = 1.39 Å Huber – Eulerian cradle

7 Virgin multilayer (Co 90 Fe 10 /Cu)  20 [Å]

8 TEM and SAED TEM at a strong overfocus SAED (diameter 250 nm)

9 Annealed multilayer (Co 90 Fe 10 /Cu)  20 t (CoFe) [nm] t (Cu) [nm] 20°C (1.16±0.12) (2.06±0.11) 235°C (1.16±0.12) (2.04±0.15) 340°C (1.19±0.13) (2.02±0.20)  (CoFe) [nm]  (Cu) [nm] 20°C (0.73±0.21) (0.88±0.20) 235°C (0.83±0.27) (1.03±0.20) 340°C (0.87±0.30) (1.15±0.30) Refined parameters XRR: = 1.37Å ;  : = 1.39 Å Interface discontinuity at 340°C

10 Annealed multilayer (Co 90 Fe 10 /Cu)  20 As prepared 235°C 340°C 111 Cu 1 hour = Å

11 Virgin multilayer (Co 90 Fe 10 /Cu 85 Ag 10 Au 5 )  20 [Å] Co 90 Fe 10 /Cu

12 Virgin multilayer (Co 90 Fe 10 /Cu 85 Ag 10 Au 5 )  20 Co 90 Fe 10 /Cu Co 90 Fe 10 /Cu 85 Ag 10 Au 5

13 Annealed multilayer (Co 90 Fe 10 /Cu 85 Ag 10 Au 5 )  20 Refined parameters t (CoFe) [nm] t (CuAgAu) [nm] 20°C (1.14±0.13) (2.09±0.11) 235°C (1.13±0.12) (2.08±0.12) 340°C (1.09±0.14) (2.11±0.14)  (CoFe) [nm]  (CuAgAu) [nm] 20°C (0.75±0.28) (0.89±0.20) 235°C (0.75±0.30) (0.93±0.25) 340°C (0.83±0.34) (1.07±0.23) No interface discontinuity at 340°C

14 Annealed multilayer (Co 90 Fe 10 /Cu 85 Ag 10 Au 5 )  20 As prepared 235°C 340°C 111 Cu 1 hour

15 Structure model for Co 90 Fe 10 /Cu Cu CoFe Cu CoFe annealing Cu CoFe Cu Increase of interface roughness. Onset of interface discontinuity.

16 Structure model for Co 90 Fe 10 /Cu 85 Ag 10 Au 5 Cu(Au) CoFe annealing Cu Ag Increase of interface roughness. Separation of gold and silver. Au

17 Conclusions n Annealing at 235°C initiated out-diffusion of Co and Cu and an increase of the interface roughness in both systems  still, the GMG effect was improved n Annealing at higher temperatures led to degradation of the multilayer structure and to the decrease of GMR: – Co 90 Fe 10 /Cu – discontinuity of interfaces – Co 90 Fe 10 /Cu 85 Ag 10 Au 5 – precipitation of Ag and Au at the surface (Ag) and within the layers (Au)