Methods for making hydrothermally crystallized water-dispersible hexaferrite platelets

Abstract

Some variations provide a method of making water-dispersed hexaferrite nanoparticles, comprising: providing a first salt containing iron, a second salt containing barium and/or strontium, and a third salt containing an anion or cation that is capable of forming a ligand with the hexaferrite nanoparticles; combining the first salt, second salt, third salt, and water to form a reaction mixture; subjecting the reaction mixture to effective reaction conditions to produce hexaferrite nanoparticles with the anion or cation in the third salt forming a ligand on the surface, so that the hexaferrite nanoparticles are dissolved and/or suspended in the reaction mixture; and obtaining water-dispersed hexaferrite nanoparticles with an average zeta potential of at least ±20 mV. The water-dispersed hexaferrite nanoparticles have a hexaferrite content of at least 85 wt %. The method may further include assembling water-dispersed hexaferrite nanoparticles into a magnetic component, such as a self-biased hexaferrite film on a semiconductor substrate.