Interface Driven Effects in Magnetization-Induced Optical Second Harmonic Generation in Layered Films Composed of Ferromagnetic and Heavy Metals.

Evgeniy Mamonov,Alexei Temiryazev,Marina Temiryazeva,Igor Pashen’Kin,Irina Kolmychek,Nikita Gusev,Tatiana Murzina,Victoria Radovskaya,Anton Maydykovskiy

doi:10.3390/ma14133573

Abstract

Properties of nanolayers can substantially differ from those of bulky materials, in part due to pronounced interface effects. It is known that combinations of layers of heavy and ferromagnetic metals leads to the appearance of specific spin textures induced by interface-induced Dzyaloshinskyi–Moria interaction (DMI), which attracts much interest and requires further studies. In this paper, we study magneto-optical effects in two- and three-layer films composed of a few nanometer thick Co layer adjacent to nanofilms of non-magnetic materials (Pt, W, Cu, Ta, MgO). For experimental studies of the interface magnetization-induced effects, we used the optical second harmonic generation (SHG) technique known for its high sensitivity to the symmetry breaking. We found that the structural asymmetry leads to the increase of the averaged SHG intensity, as well as to the magnetic field-induced effects in SHG. Moreover, by choosing the proper geometry of the experiment, we excluded the most studied linear in magnetization SHG contributions and, thus, succeeded in studying higher order in magnetization and non-local magnetic effects. We revealed odd in magnetization SHG effects consistent with the phenomenological description involving inhomogeneous (gradient) magnetization distribution at interfaces and found them quite pronounced, so that they should be necessarily taken into account when analyzing the non-linear magneto-optical response of nanostructures.

Highlights

Structuring of a medium at nanoscale can give rise to new effects in their optical and magnetic response [1,2]
This technique was applied for the investigation of layered structures made of cobalt and heavy metals (Ta, Pt), which were expected to reveal interface Dzyaloshinskyi–Moria interaction; it was shown that besides common magnetooptical effects at the second harmonic generation (SHG) wavelength (MOKESHG), extra one intensity effect forbidden for homogeneously magnetized interfaces was observed [15,16]
We studied experimentally the appearance of magneto-optical effects accompanying second harmonic generation in two- and three-layer films containing ferromagnetic cobalt layers adjacent to different non-magnetic specimen

Summary

Introduction

Structuring of a medium at nanoscale can give rise to new effects in their optical and magnetic response [1,2]. It was demonstrated that the SHG probe allows to reveal specific magnetic ordering, such as antiferromagnetic or vortex states [12,13,14] This technique was applied for the investigation of layered structures made of cobalt and heavy metals (Ta, Pt), which were expected to reveal interface Dzyaloshinskyi–Moria interaction; it was shown that besides common magnetooptical effects at the SHG wavelength (MOKESHG), extra one intensity effect forbidden for homogeneously magnetized interfaces was observed [15,16]. In order to study further this non-linear-optical effect, in this work we present a complex analysis of nonlinear magneto-optical effects in nanolayered magnetic films composed of the ferromagnetic metal (Co)and a much wider variety of non-magnetic materials (Pt, Ta, W, Cu, MgO)

Results

Discussion

Conclusion