Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Abstract: C1.00185 : Exchange constants and spin waves of MnV$_{2}$O$_{4}$ from first principles DFT calculations
Author:
We present results of DFT calculations of exchange constants of
the magnetic
spinel MnV$_{2}$O$_{4}$. The starting point is the one-particle
eigenfunctions of the Kohn-Sham auxiliary Hamiltonian as a
function of the
self-consistent, converged charge density. Using linear response and
perturbation theory, the exchange constants between the magnetic
ions Mn and
V are calculated in both the collinear and non-collinear,
orbital-ordered
phases of the spinel. The collinear exchanges have exchange
constants
proportional to the unit matrix, which means they are isotropic.
On the
other hand, the non-collinear exchanges have unequal diagonal
elements and
in addition have off-diagonal elements, revealing anisotropic
magnetic
interactions. The anisotropy is traced to the orbital-order and
non-collinear spin structure of the low-temperature ground-state.
We find
that the interactions between the V atoms can sometimes be
anti-ferromagnetic. The V atoms are located at the vertices of a
corner-sharing tetrahedral lattice, commonly known as a
pyrochlore lattice.
AFM interactions on such a lattice are geometrically frustrated
because all
pair-wise bond energies cannot be simultaneously minimized with a
classical
spin configuration. It has been experimentally found that as the
temperature
is lowered, MnV$_{2}$O$_{4}$ undergoes a transition from a
paramagnet with a
cubic symmetry structure phase to a ferrimagnetic with cubic
symmetry phase
at 56 K.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.C1.185
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