Structural, magnetic, and nanoacoustic characterization of Co/Pt superlattices

TL;DR

This study investigates the structural, magnetic, and nanoacoustic properties of Pt/Co superlattices, revealing their potential for ultrahigh-frequency magnetoacoustic device applications through detailed characterization and acoustic mode analysis.

Contribution

It provides a comprehensive analysis of Pt/Co superlattices, highlighting their composition modulation, magnetic anisotropy, and support for high-frequency acoustic modes, advancing nanoacoustic device research.

Findings

Superlattices have well-defined periodicity with compositional modulation.

Samples support acoustic modes up to 900 GHz.

Magnetization shows perpendicular magnetic anisotropy at higher Co concentrations.

Abstract

Superlattices presenting a spatial modulation of the elastic properties appear as a main tool to reach the THz regime in nanoacoustic devices. The exploration of alternative materials with multifunctional properties remains a fertile domain of research. In this work, we study the structural, magnetic, and acoustic characteristics of nanometric superlattices made of Pt/Co. The samples present a well defined periodicity, as determined by X-ray reflectometry, whereas scanning transmission electron microscopy with local compositional analysis reveals that the superlattices present a modulation in composition instead of sharp interfaces. The policrystalline nature of the superlattices is evidenced both by X ray diffraction and transmission electron microscopy. Magnetization measurements show a perpendicular magnetic anisotropy for the higher Co concentrations. Picosecond acoustic experiments evidence that the studied samples support short-lived acoustic modes up to 900 GHz, and up to 7 acoustic echoes at lower frequencies.These are promising results for the development of magnetoacoustic devices working at ultrahigh frequencies.