Calculations of i nterplay between anizotropy and coupling energy in magnetic multilayers systems

1. Calculations of interplay between anizotropy and coupling energy in magneticmultilayerssystems M.Czapkiewicz Department of Electronics, AGH University of Science and Technology, POLAND

2. Schedule • one-domain S-W model • MAGEN2 - program for simulation of magnetization process of multilayers systems • examples of calculations and experiments • PSV • SV • Biased FP • TMR SV • SV AAF • To-do tasks

3. Definitions • Magnetization: monolayer bilayer • AMR (ML) • GMR (BL) Task to compute: how  depend on H ?

4. Stoner-Wohlfarth model • Surface energy density (example for 2 layers with planar UA anisotropy): where • Numerical gradient seeking of local minimum for each H field

5. Program interface • Input: • Saturation magnetization • Effective anisotropy energy • Anisotropy axis definition • Interlayer coupling energy • Field range • Output: •  angles for each layer • Total magnetization M(H) • Total energy • To do: GMR, TMR…

6. example – PSV-type bilayer Measured example: Py2.8nm/Co2.1nm/Cu2nm/Co3nm Fit for: Ku1/Ku2 = 31 GMR only in non-parallel state

7. Influence of ferromagnetic coupling on PSV switching AF-state only if JFF weak

8. 2. example – SV with AF layer Measured sample: Co4.4nm/Cu2.3nm/Co4.4nm/FeMn10nm exchange coupling energy JFP-FF= 7.910-6 J/m2 interface coupling energy JEB = 9410-6 J/m2 anisotropy energy KFF= 580 J/m3, effective AF anizotropy KAF= 80·103 J/m3

9. Influence of FP-FF ferromagnetic coupling on GMR of SV structure • Analytical simulation for

10. 3. Influence of effective anisotropy of AF layer on SV biased field M.Tsunoda model: ordering of AF layer grains (during deposition for top-type SV or during field cooling for bottom-type SV) lead to increase total eff. anisotropy Energy density model of AF-FP system:

11. Example of AF-FP system (after f.c.) Si/Ta5nm/Cu10nm/Ta5nm/NiFe2nm/Cu5nm/MnIr10nm/CoFe2,5nm annealed: 200oC/1h, field cooling 1kOe CoFe – 25 Å MnIr – 100Å fit for: JEB= 20010-6 J/m2 , KAF= 40000 J/m3. Courtesy of Prof. C.G. Kim Chungnam University RECAMM, Taejon, Korea

12. 4. Influence of KAF to JEB ratio of FF/S/FF/AF structure on M(H) switching

13. Dependence of HEB on KAF

14. 4. MTJ example Buffer:Si/Ta5nm/Cu10nm/Ta5nm/Ni80Fe202nm/Cu5nm AF layer: Ir25Mn75 (10nm), FP layer Co70Fe30 (2.5nm), isolator spacer and FF layer AlOx(1.5nm)/Co70Fe30(2.5nm)/Ni80Fe20 (10nm) Fit for: anizotropy energy of FF layer K1= 210 J/m3, m0 Ms1 = 0.85 T, exchange coupling energy FF-FP J12= 1.0410-6 J/m2(FF). effective anizotropy energy of FP layer K2= 95000 J/m3, m0 Ms2 = 1.5 T, interface coupling energy FP-AF JEB=47010-6 J/m2. effective anizotropy energy of AF layer KAF= 50000 J/m3

15. 5. SV with Artificial AF – before annealing AFF-SV: AF/FP1/S1/FP2/S2/FF Example: Si(111)/Ta10.5nm/PtMn19.8nm/ CoFe2nm/Ru0.77nm/CoFe2nm/ Cu2.2nm/CoFe0.8nm/NiFe3.8nm/ Ta5nm/Cu0.5nm

16. “To do” list for MAGEN2 program • bugs fixing • experimental data in background • more layers • 3D axis of anisotropy and field definition • animation of magnetisation vector of each ferromagnetic layer during simulation process • GMR/TMR characteristics

17. END

18. S-W model for monolayer • Total energy E = EH+ EU + ED • Zeeman energy • Anisotropy energy • Demagnetizing energy Field in plane (Nx=Ny0, Nz1):

19. 4. Example of Magnetic Tunneling Junction Energy density model: Ta – 50Å NiFe – 100Å CoFe – 25 Å Al2O3 – 15 Å CoFe – 25 Å MnIr – 100Å Cu – 50 Å NiFe – 20 Å Ta – 50 Å Cu – 100 Å Ta – 50 Å Substrate Si (100)