The effect of Microstructure in Exchange Decoupling of SmCo5/Co bi-layers at low temperatures

TL;DR

This study examines how microstructure, specifically grain size and crystallinity, influences exchange decoupling in SmCo5/Co bi-layers at low temperatures, revealing that substrate-induced grain differences affect magnetic coupling.

Contribution

It demonstrates how substrate choice affects grain formation and magnetic properties, providing insights into low-temperature exchange decoupling mechanisms in SmCo5/Co bi-layers.

Findings

SmO(100) substrate yields smaller, uniform grains

High crystallinity correlates with better magnetic properties

Large grains on glass reduce inter-grain exchange coupling

Abstract

Here, we investigated the influence of grain formation on the magnetization reversal of SmCo5/Co at low temperature. A set of SmCo5/Co bi-layer samples were fabricated under identical conditions on MgO(100) and glass substrates with a Cr underlayer. Analysis of each magnetic layer by an Atomic Force Microscope (AFM) reveals that MgO(100) results small and uniform grain formation of 23 nm in contrast to 57 nm on glass, and x-ray diffraction studies show that the sample on MgO(100) has high crystallinity with SmCo5(11 0) phase. At room temperature, both samples exhibit good hard magnetic properties with coercivity (HC) of 13.2 kOe and 12.5 kOe, and energy products (BH)max of 14.5 MGOe and 5.3 MGOe for samples on MgO(100) and glass, respectively. Low temperature hysteresis measurements show an exchange decoupling at low temperatures for the sample on glass, and this is due to the formation of large grains on glass that reduces the effective inter-grain exchange coupling between phases.