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

Kirk, SR 2001, Ab initio study of magnetic anisotropy of M-type hexaferrite thin films , PhD thesis, University of Salford.

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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.

Item Type: Thesis (PhD)
Contributors: Gerber, R (Supervisor)
Schools: Schools > School of Computing, Science and Engineering
Depositing User: USIR Admin
Date Deposited: 18 Jul 2022 09:17
Last Modified: 18 Jul 2022 09:17
URI: https://usir.salford.ac.uk/id/eprint/64420

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