Magnetic Polaron Formation Dynamics in Mn2+-Doped Colloidal Nanocrystals up to Room Temperature

Gerd Bacher, Lars Schneider, Rémi Beaulac, Paul I. Archer and Daniel R. Gamelin

J. Korean Phys.Soc. 58,1261 [doi: 10.3938/jkps.58.1261 | PDF Download]

The dynamics of exciton magnetic polaron (EMP) formation after pulsed laser excitation is studied in Mn2+-doped colloidal CdSe nanocrystals. A transient energy shift of more than 130 meV at low temperature is obtained for the characteristic photoluminescence signal, and is related to the alignment of the Mn2+-ion spins in the exchange field of the optically generated electron-hole pairs. The dynamics of laser induced magnetization are characterized by at least two time constants attributed to the EMP formation within a few hundreds of picoseconds, followed by a subsequent reorientation of the EMP spin complex in the nanosecond regime. We found a complete spin alignment up to temperatures of about 50 K and clear signatures of optically induced magnetization up to room temperature.