Epitaxial Nd-Fe-B films: Growth, texture, magnetism and the influence of mechanical elongation

Beschreibung

The work in this thesis focuses on the preparation of epitaxial Nd-Fe-B thin films using pulsed
laser deposition for good hard magnetic properties. They are suitable for a basic understanding
of the intrinsic magnetic properties. Compositional control was necessary to achieve phase
formation with improved magnetic properties. Nd-Fe-B samples were prepared on single
crystal MgO (001) substrates with different buffer layers in order to obtain good textures with
different surface morphology.
The smooth and continuous epitaxial films were suitable for performing magnetization
measurements under stress. Although the magnetostriction is easily neglected in the Nd2Fe14B
compound, distinguishable inverse magnetostriction was observed by conventional tensile
elongation with a flexible substrate. As a result, anisotropic strain in the film, which breaks the
in-plane symmetry, affected the opening angle during the spin reorientation. Therefore an
elliptical distortion of the in-plane anisotropy below the spin reorientation temperature of
Nd2Fe14B was obtained, whereas the transition temperature itself was not influenced
significantly.