Core-shell nanostructure in a Ge_0.9Mn_0.1 film from structural and magnetic measurements

TL;DR

This study characterizes the structural and magnetic properties of Ge_0.9Mn_0.1 films with self-organized Mn-rich nanocolumns, revealing a core-shell phase separation important for transition-metal doped semiconductors.

Contribution

It provides detailed structural and magnetic analysis of core-shell nanocolumns in Ge_0.9Mn_0.1 films using advanced microscopy and magnetic measurements, highlighting phase separation.

Findings

Nanocolumns form a triangular lattice with Mn-rich cores and shells.

No Mn atoms detected in the Ge matrix outside the nanocolumns.

Core-shell phase separation influences magnetic properties.

Abstract

We have characterized a film of Ge_0.9Mn_0.1 forming self-organized nanocolumns perpendicular to the Ge substrate with high resolution scanning transmission electron microscopy combined with electron energy loss spectroscopy, and bulk magnetization and positive muon spin rotation and relaxation (muSR) measurements. The Mn-rich nanocolumns form a triangular lattice with no detectable Mn atoms in the matrix. They consist of cores surrounded by shells. The combined analysis of bulk magnetization and muSR data enables us to characterize the electronic and magnetic properties of both the cores and shells. The discovered phase separation of the columns between a core and a shell is probably relevant for other transition-metal doped semiconductors.