Ab initio study of magnetic anisotropy of M-type hexaferrite thin films

Kirk, SR

Abstract

Ferrites are a broad class of oxide materials with a wide range of
technologically important applications. The M-type hexaferrites, of
which BaFe12O19 is taken as a prototype compound, show particular promise as very high density magnetic and magneto-optical data
storage media. There are still serious gaps in the understanding of
the fundamental origins of, and mechanisms governing, the magnetic
properties of these materials. The detailed relationships between these
properties and the material structure over nanometre length scales are
also not fully understood. This thesis addresses both of these pressing
issues. It describes first a detailed ab initio theoretical treatment of
the origins and magnitudes of the two most important mechanisms
which give rise to magnetic anisotropy, namely dipolar interactions
and single-ion contributions. The thesis outlines the theory of these
two types of magnetic interactions in solid insulating oxide materials.
It also describes the theory of the deposition and growth of thin films,
and the implementation of both branches of this theoretical study
in a set of original computer programs developed and refined during
this study, comprising tools for both calculation and visualization. A
novel growth model and efficient Monte Carlo techniques are used to
investigate and quantify the dependence on growth conditions of the
structure of thin films of hexaferrite materials. The magnetic theory is also implemented in a flexible and powerful program, which is
used in turn to comprehensively investigate the structural dependence
of magnetic properties in the bulk crystalline material, idealized thin
films, and finally by the simulated grown films. The influence of film
structure on volume and surface contributions to the anisotropy of
thin films is thereby quantified and discussed.

Citation

Kirk, S. Ab initio study of magnetic anisotropy of M-type hexaferrite thin films. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Jul 18, 2022
• Publicly Available Date: Jul 18, 2022
• Award Date: Jul 1, 2001