A ferromagnetic Eu-Pt surface compound grown below hexagonal boron nitride

TL;DR

This study demonstrates that Eu intercalation under hBN on Pt creates a ferromagnetic EuPt$_2$ surface alloy with partial air stability, revealing insights into 2D protective layers for reactive metals and their ambient resilience.

Contribution

It reports the formation of a ferromagnetic EuPt$_2$ surface alloy via Eu intercalation under hBN on Pt and analyzes its stability and properties under ambient conditions.

Findings

Eu intercalation forms a ferromagnetic EuPt$_2$ surface alloy.

Partial preservation of Eu$^{2+}$ state after air exposure.

Ambient pressure effects vary with substrate curvature and surface roughness.

Abstract

One of the fundamental applications for monolayer-thick 2D materials is their use as protective layers of metal surfaces and in-situ intercalated reactive materials in ambient conditions. Here we investigate the structural, electronic, and magnetic properties, as well as the chemical stability in air of a very reactive metal, Europium, after intercalation between a hexagonal boron nitride (hBN) layer and a Pt substrate. We demonstrate that Eu intercalation leads to a hBN-covered ferromagnetic EuPt$_2$ surface alloy with divalent Eu$^{2+}$ atoms at the interface. We expose the system to ambient conditions and find a partial conservation of the di-valent signal and hence the Eu-Pt interface. The use of a curved Pt substrate allows us to explore the changes in the Eu valence state and the ambient pressure protection at different substrate planes. The interfacial EuPt$_2$ surface alloy formation remains the same, but the resistance of the protecting hBN layer to ambient conditions is reduced, likely due to a rougher surface and a more discontinuous hBN coating.