Physical property relationships in spinel ferrite thin films developed using the spin-spray deposition method

Recently, a great deal of attention has gone into tunable materials such as spinel ferrites, carbon nanotube composites (CNT), and barium strontium titanate (BST). In this study, we discuss the physical properties of tunable thin films (about 1 μm thick) of Ni-Zn ferrites in relation to their dynamic electromagnetic properties. The spinel ferrites are deposited by aqueous spin-spray plating, at temperatures as low as 90°C. Using this technique the typical grain sizes are around 55 nm which is generally much smaller than found in conventional bulk ferrites. Moreover, there is additional complexity due to a multi-level, multi-scale hierarchy of texturing in how the grains pack. Due to the small grain size, we have shown that one magnetic domain is often comprised of multiple physical grains and is about 236 nm in width. This opposite of what is found in bulk grain magnetic materials where each physical grain contains multiple magnetic domains. It is this multigrain magnetic domain structure that contributes to an enhanced combination of high permeability and high resonance frequency.