Magneto-Optical Properties of Small Atomic Clusters of Ga and In with As, V and Mn
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Magneto-Optical Properties of Small Atomic Clusters of Ga and In with As, V and Mn Liudmila A. Pozhar1, Alan T. Yeates2, Frank Szmulowicz2 and William C. Mitchel2 1
Western Kentucky University, Department of Chemistry, 1906 College Heights Blvd., Bowling Green, KY 42101, U.S.A. 2 Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, OH 45433, U.S.A.
ABSTRACT The Hartree-Fock (HF) method is used to synthesize virtually (i.e., fundamental theorybased, computationally) small stable atomic clusters of Ga and In with As and V, and an Inbased cluster with As and Mn. The electronic energy level structures (ELSs), optical transition energies (OTEs), and charge/spin density distributions of these clusters have been analyzed. It has been shown that the spin of such clusters is collectivized, and that this collectivization is responsible for a dramatic drop in the clusters’ OTEs as compared to those of similar pyramidal clusters that do not contain “magnetic” atoms.
INTRODUCTION Recently, small stable pre-designed pyramidal clusters of Ga and In atoms with As, P and V were studied in detail in the framework of the HF and multi-configuration self-consistent field (MCSCF) methods [1]. Experimental studies of the last few years [2] confirm that small clusters of Ga, In and As atoms nucleating in the process of bottom-up synthesis of nanomaterials indeed have the structure, stoichiometry and electronic properties similar to those predicted theoretically when a scaling factor is taken into account (experimentally synthesized clusters are about 10 times larger than those designed theoretically). Virtual atomic clusters containing “magnetic” atoms can be used as models to guide experimental synthesis of diluted semiconductor nanomaterials for sources and sensors, and for the use in magneto-optical memory devices. The small pyramidal clusters of the work reported below are obtained using the original predesigned and vacuum clusters Ga10As4 and In10As4 of Refs. 1, where one of As atoms is replaced by V or Mn. The HF energy minimization method has been used to synthesize the stable clusters. The pre-designed clusters have been virtually synthesized with the use of spatial constraints applied to the atomic position, to reflect nucleation of such clusters in quantum confinement, while vacuum clusters have been obtained with no spatial constraints. Virtual synthesis of other similar clusters (such as those derived from the mentioned clusters Ga10As4 and In10As4 by the replacement of any Ga or In atom with those of V or Mn) has also been attempted. However, the HF computations show that such clusters are unstable.
VIRTUAL DESIGN OF Ga- AND In- BASED CLUSTERS WITH As, V AND Mn The dimensions of the pyramidal clusters discussed below have been derived from pyramidal symmetry elements of zincblende lattices of GaAs and InAs bulk semiconductor
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materials as described in Ref. 1. The pyramid frames are constructed of ten Ga or In atoms (the covalent radii 1.26
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