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Intern: Micah Hall, University Tennessee-Knoxville Mentor: K. Ramesha Faculty Supervisor: Ram Seshadri Department: MRL

COMPUTATIONAL INVESTIGATION INTO DETERMINING THE ELECTRONIC STRUCTURE CHARACTERISTICS OF THE PEROVSKITE MATERIAL RMNO3

Curiosity in the properties of the giant magnetoresistant (GMR) perovskite material RMnO3 (R = La or Y) basically arisen from the fact that in these particular structures, there is a type of structural distortion and asymmetry with the bond lengths and angles within the MnO6 octahedra. Preliminary observations of this phenomenon have shown that this anomaly is due to a Jahn-Teller (J-T) distortion of the orbital arrangement within MnO6. To further explore this phenomenon, a series of computational calculation were performed. These calculations can accurately generate diagrams called the density of states diagram and electronic band diagrams. After obtaining a representation of the up and down spin orientations of the electrons for the materials LaMnO3 and YMnO3 with the density of states diagram, it clearly demonstrates that these materials have magnetic properties and similar structural characteristics. For the electronic band diagrams, emphasis was centered on the orbital region dz2 because of the distortion of the orbitals in the z-direction. After evaluating these diagrams, both of the materials reflected having properties of a semiconductor and it can be seen that the width of the bands in YMnO3 is slightly less than for LaMnO3 resulting in the larger J-T distortion.

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