Tuning the interlayer coupling in La0.7Sr0.3Mn0.95Ru0.05O3 / LaNiO3 multilayers with perpendicular magnetic anisotropy

TL;DR

This study investigates how varying the thickness of LaNiO3 spacers in La0.7Sr0.3Mn0.95Ru0.05O3 / LaNiO3 multilayers affects interlayer magnetic coupling and anisotropy, revealing a transition from antiferromagnetic to ferromagnetic coupling.

Contribution

It demonstrates control over interlayer magnetic coupling and anisotropy in ferromagnetic oxide multilayers by tuning spacer thickness, with detailed magnetic characterization.

Findings

Coupling switches from antiferromagnetic to ferromagnetic with spacer thickness.

Magnetic order in LNO spacer closely follows adjacent LSMRO layers.

Effective magnetic anisotropy changes, causing magnetization canting.

Abstract

In ferromagnetic oxide epitaxial multilayers, magnetic properties and interlayer coupling are determined by a variety of factors. Beyond the contribution of interlayer exchange coupling, strain and interfacial effects, such as structural reconstructions or charge transfer, play significant roles, resulting in complex magnetic behaviour. In this study the interlayer coupling of ferromagnetic La0.7Sr0.3Mn0.95Ru0.05O3 (LSMRO) layers (8 nm thick) was investigated, when separated by epitaxial spacers of paramagnetic metallic LaNiO3 (LNO), in stacks exhibiting perpendicular magnetic anisotropy. By varying the thickness of the spacer, it was found that the coupling between two LSMRO layers changes from antiferromagnetic (with a 4 unit cell thick LNO spacer) to ferromagnetic (with a 6 unit cells thick LNO spacer). For multilayers comprising five LSMRO layers and a 4 unit cell thick LNO spacer, the antiferromagnetic coupling was preserved. However, the effective magnetic anisotropy changed, causing the magnetization to cant more towards the in-plane direction. This behavior was corroborated by X-ray magnetic circular dichroism (XMCD) investigations at the Mn and Ni L3-edges. The XMCD results indicated that the 4 unit cells thick LNO spacer in the multilayer become magnetically ordered, closely following the magnetization of adjacent LSMRO layers.