Influence of Thickness on Magnetic Properties and Microwave Characteristics of NiFe/IrMn/NiFe Trilayers

Exchange-bias effect is effective in in creasing the ferromagnetic resonance frequency of soft magnetic thin films. This paper studies the static magnetic properties and microwave characteristics of Ni
₈₁
Fe
₁₉
/Ir
₂₅
Mn
₇₅
/Ni
₈₁
Fe
₁₉
trilayers with various Ni
₈₁
Fe
₁₉
and Ir
₂₅
Mn
₇₅
thicknesses. With an ultrathin Ir
₂₅
Mn
₇₅
interlayer, the trilayer has an enhanced effective damping without exchange-bias effect. The exchange-bias effect is observed with a thicker Ir
₂₅
Mn
₇₅
interlayer. The two resonance frequencies in permeability spectra are due to the different interfacial exchange couplings at the two interfaces of trilayers, and they increase with decreasing Ni
₈₁
Fe
₁₉
layer thickness.