title: Tunable magnetic exchange interactions in manganese-doped inverted core-shell ZnSe-CdSe nanocrystals.
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 through growth-controlled 'engineering' of electron and hole wavefunctions in 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(2+)-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 used to manipulate carrier-Mn(2+) wavefunction overlap and the sp-d exchange parameters themselves.
authors.affiliation: Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Bussian
authors.forename: Scott A
authors.initials: SA
authors.lastname: Crooker
authors.forename: Ming
authors.initials: M
authors.lastname: Yin
authors.forename: Marcin
authors.initials: M
authors.lastname: Brynda
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Efros
authors.forename: Victor I
authors.initials: VI
authors.lastname: Klimov