Tunable magnetic exchange interactions in manganese-doped inverted core/shell ZnSe/CdSe nanocrystals

TL;DR

This study demonstrates that the magnetic exchange interactions in manganese-doped core/shell ZnSe/CdSe nanocrystals can be widely tuned by adjusting the shell thickness, enabling control over exciton spin properties for spintronic applications.

Contribution

It introduces a method to controllably tune the sp-d exchange interaction in heterostructured nanocrystals through shell engineering, revealing tunable Zeeman splittings and exciton g-factors.

Findings

Zeeman spin splittings are tunable in magnitude and sign.

Exciton g-factors can be controlled from -200 to +30.

Wavefunction engineering affects carrier-Mn interactions.

Abstract

Magnetic doping of semiconductor nanostructures is actively pursued for applications in magnetic memory and spin-based electronics. Central to these efforts is a drive to control the interaction strength between carriers (electrons and holes) and the embedded magnetic atoms. In this respect, colloidal nanocrystal heterostructures provide great flexibility via growth-controlled `engineering' of electron and hole wavefunctions within individual nanocrystals. Here we demonstrate a widely tunable magnetic sp-d exchange interaction between electron-hole excitations (excitons) and paramagnetic manganese ions using `inverted' core-shell nanocrystals composed of Mn-doped ZnSe cores overcoated with undoped shells of narrower-gap CdSe. Magnetic circular dichroism studies reveal giant Zeeman spin splittings of the band-edge exciton that, surprisingly, are tunable in both magnitude and sign. Effective exciton g-factors are controllably tuned from -200 to +30 solely by increasing the CdSe shell thickness, demonstrating that strong quantum confinement and wavefunction engineering in heterostructured nanocrystal materials can be utilized to manipulate carrier-Mn wavefunction overlap and the sp-d exchange parameters themselves.