Intrinsic Ferromagnetic Semiconductors: Rare-Earth Mononitrides
Event details
| Date | 16.12.2013 |
| Hour | 14:15 |
| Speaker |
Prof. Joe Trodahl, Victoria University of Wellington Bio: Joe's current research interests are a colourful mix of different topics including studies of the rare-earth nitrides and Raman spectroscopy applied to a wide variety of materials. Joe's work involves collaboration with numerous students, postdocs, and academics at VUW and the MacDiarmid Institute, and at other institutions in New Zealand and around the world. |
| Location | |
| Category | Conferences - Seminars |
For a decade from the late 1990s there was an intense effort on diluted ferromagnetic semiconductors (DMS), aimed largely to raise their Curie temperature to ambient. The interest continued for so long despite that the heavy doping, typically 5-10% in, for example, (Ga,Mn)As rendered them degenerately hole doped. Intrinsic ferromagnetic semiconductors would offer even more hope of active devices with well-defined transport in spin-selected channels. However, there are remarkably few such semiconductors.
The nitrides of the rare earth elements are an attractive exception. The adopt the NaCl structure with epitaxial compatibility both across the series and with the III-nitrides. Most of the fourteen examples are ferromagnetic and the half that have been well characterised are all semiconductors. The lack of orbital quenching, as is familiar in transition metal compounds, leads to significant and sometimes dominating orbital contributions to their magnetic moments, which in turn gives them a range of strongly contrasting magnetic and magnetotransport behaviours. Like the DMS systems they display ferromagnetism only well below ambient temperature; but their dope-able transport offers promise.
This presentation will describe our REN programme, based on growth of both homogeneous and multilayered films. They are investigated by conventional magnetic, magnetotransport and optical/X-ray spectroscopies to determine their spin-split band structure and the atomic shell-resolved magnetic moments. Special attention will be given to the pure spin moment in GdN, the nearly perfect cancellation of spin and orbital ferromagnetic moments in SmN and the DMS behaviour of normally nonmagnetic EuN.
The nitrides of the rare earth elements are an attractive exception. The adopt the NaCl structure with epitaxial compatibility both across the series and with the III-nitrides. Most of the fourteen examples are ferromagnetic and the half that have been well characterised are all semiconductors. The lack of orbital quenching, as is familiar in transition metal compounds, leads to significant and sometimes dominating orbital contributions to their magnetic moments, which in turn gives them a range of strongly contrasting magnetic and magnetotransport behaviours. Like the DMS systems they display ferromagnetism only well below ambient temperature; but their dope-able transport offers promise.
This presentation will describe our REN programme, based on growth of both homogeneous and multilayered films. They are investigated by conventional magnetic, magnetotransport and optical/X-ray spectroscopies to determine their spin-split band structure and the atomic shell-resolved magnetic moments. Special attention will be given to the pure spin moment in GdN, the nearly perfect cancellation of spin and orbital ferromagnetic moments in SmN and the DMS behaviour of normally nonmagnetic EuN.
Practical information
- Informed public
- Free
Organizer
- ICMP (Arnaud Magrez and Raphael Butté)
Contact
- Arnaud Magrez