Magnetodipolar interlayer interaction effect on the magnetization dynamics of a trilayer square element with the Landau domain structure

Abstract

We present a detailed numerical simulation study of the effects caused by the magnetodipolar interaction between ferromagnetic (FM) layers of a trilayer magnetic nanoelement on its magnetization dynamics. As an example we use a Co/Cu/Ni80Fe20 element with a square lateral shape where the magnetization of FM layers forms a closed Landau-like domain pattern. First we show that when the thickness of the non-magnetic (NM) spacer is in the technology relevant region h ~ 10 nm, magnetodipolar interaction between 90o Neel domain walls in FM layers qualitatively changes the equilibrium magnetization state of these layers. In the main of the paper we compare the magnetization dynamics induced by a sub-nsec field pulse in a single-layer Ni80Fe20 (Py) element and in the Co/Cu/Py trilayer element. Here we show that (i) due to the spontaneous symmetry breaking of the Landau state in the FM/NM/FM trilayer its domains and domain walls oscillate with different frequencies and have different spatial oscillation patterns; (ii) magnetization oscillations of the trilayer domains are strongly suppressed due to different oscillation frequencies of domains in Co and Py; (iii) magnetization dynamics qualitatively depends on the relative rotation sense of magnetization states in Co and Py layers and on the magnetocrystalline anisotropy kind of Co crystallites. Finally we discuss the relation of our findings with experimental observations of magnetization dynamics in magnetic trilayers, performed using the element-specific time-resolved X-ray microscopy.