AVS 51st International Symposium
    Magnetic Interfaces and Nanostructures Tuesday Sessions
       Session MI-TuP

Paper MI-TuP5
Rotational Loss in Exchange Bias Systems and their Modeling

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: K. Steenbeck, IPHT Jena, Germany
Authors: K. Steenbeck, IPHT Jena, Germany
R. Mattheis, IPHT Jena, Germany
M. Diegel, IPHT Jena, Germany
Correspondent: Click to Email
The rotational loss E in sputtered AF/F systems (AF: IrMn, thickness t = 0 to 13 nm, F: NiFe, CoFe, CoFe/Cu, thickness about 18 nm) is determined in dependence on AF thickness t by torquemetry at high field and at 10 and 300 K. After onset of E at low thickness a huge loss peak occurs at that thickness where exchange bias starts to develop and goes down to a lower and constant value above a critical thickness t@sub c@. Our simulations are based on a statistical distribution of coupling energies and include new aspects not considered up to now. For the first time rotational loss can be calculated in (111) textured films and the complete thickness dependence of E(t) can be described. Below t@sub c@ we consider crystallites with homogeneous AF magnetization, a 3-axial AF anisotropy K and an AF interface net moment which undergoes irreversible switching for critical values j/Kt. This loss disappears for large t. For t above t@sub c@ we include domain walls parallel to the F/AF interface. Our calculations display that the main loss contribution at that thickness is caused by complete AF 60 ° domain walls created in crystallites with 3-axial anisotropy and strong enough coupling (j above 1.5 @sigma@, @sigma@ domain wall energy). Switching processes of partial domain walls in crystallites having their j/@sigma@ in a critical interval contribute only at low level. The modelling allows to derive numerical values for the coupling energy per spin, the AF anisotropy constant K and the AF domain wall energy @sigma@.