Structures and ferromagnetic properties of dilute magnetic semiconductors studied by x-ray absorption fine structure and first principles

Thursday 23 Jul 2009, 14:30 → 16:00 Europe/Rome

Auditorium B. Touschek (Laboratori Nazionali di Frascati, Via Enrico Fermi 40, Frascati)

ABSTRACT

X-ray absorption fine structure spectroscopy (XAFS) and first principles calculations may be combined to investigate the local and electronic structures of dilute magnetic semiconductors (DMS) to shed light on the ferromagnetism origin for a variety of materials. The results of Mn:ZnO and (Mn,N):ZnO thin films reveal that either the existence of Zn vacancy or N substitution of O sites can stabilize the ferromagnetic interactions between neighboring Mn-Mn pairs, and enhance the magnetic moment per Mn. For Co:ZnO thin films, the local structure around the Co atoms is strongly dependent on the growth conditions and doped ion concentrations. The substitutional Co ions are easily to gather together via intervening oxygen atoms, rather than distribute themselves randomly in the lattice. Thanks to new experimental data and theoretical calculations we propose here an original pathway to understand the microscopic origin of ferromagnetism in DMS materials.