Dr. Meichun
Qian
Title: An Ab Initio Investigation on the Half-Metallicity
of the Transition Metal Compounds with Zinc-Blende
Structure
The successful
growth of zinc-blende half-metallic compounds [1],
namely CrAs, in thin film forms offers a new
direction to search for novel spintronic materials.
Half metallicity means that the compounds have the
100% spin polarization at the Fermi level. By first-principles calculations, we
have examined the half metallicity of the transition
metal compounds with zinc-blende structure in the
form of bulk, superlattice and quantum dot. Several
transition metal compounds are predicted to exhibit the half metallic behaviors
[2]. We discuss the electronic and magnetic properties based on analyzing the effects
of hybridization between the d-states of the cation
atom and the p-states of the anion atom, the crystal field effect on the
d-manifold, and the exchange splitting of the majority and the minority spin
states. The superlattices are explored to consist of
alternating layers with two half metallic compounds and to combine with III-V semiconductors.
We investigate variable thicknesses for the combinations. The half-metallic
properties of superlattice are found to be crucially
dependent on the completion of the d-p hybridization. Finally, we study the
magnetic and structural stability for the zinc-blende
MnAs nanocrystallite. The
ferromagnetic nanocrystallite is shown to have the
characteristics of a half-metal with a large magnetic moment 4 $\mu_{B}$ per Mn
atom. The Mn-As bondlength
is slightly longer than the one in the bulk, in accord with experimental
observation.
[1]
H. Akinaga, T. Manago and
M. Shirai, Jpn. J. Appl. Phys. 39, L1118 (2000).
[2] J.E. Pask, L.H. Yang, C.Y. Fong, W.E. Pickett, and S. Dag, Phys. Rev, B67, 224420 (2003).