Rapid Formation of a Monolayer of Oriented Hard‐Magnetic Strontium Hexaferrite Nanoparticles on a Solid Substrate

Abstract

Single crystal nanoplatelets of M-type strontium hexaferrite, which were prepared by oxide glass crystallization, form colloidal solutions after consequent leaching and peptization of the nanocrystalline material. The colloids are stabilized by the particles charging to a zeta-potential of about 50 mV. Monolayers of oriented platelet strontium hexaferrite nanoparticles form readily on a glass surface while immersing the substrate in the colloidal solution due to Columb attraction of the positively charged nanoparticles to the negatively charged surface. The films show almost rectangular magnetization hysteresis loops typical for strongly textured hard-magnetic material.

Spray-Deposited Anisotropic Ferromagnetic Hybrid Polymer Films of PS-b-PMMA and Strontium Hexaferrite Magnetic Nanoplatelets

“…To address this challenge, M-type hexaferrite magnetic nanoplatelets with high coercivity can be utilized. , They are hard magnetic materials with a platelet-like shape and a high magnetic anisotropy . Earlier works showed that coercivity depended on a favorable orientation of the magnetic nanoplatelets. , To achieve the favorable orientation of the nanoplatelets, various approaches, such as anodic aluminum oxide (AAO) template, electrostatic attraction, and external magnetic field, were used. − For instance, Lukatskaya et al successfully controlled the arrangement of aluminum-doped magnetic strontium hexaferrite nanoplatelets by using the AAO membrane as a template . Kushnir et al prepared strontium hexaferrite nanoplatelets with positive charges and observed a fixed orientation of the nanoplatelets on a negatively surface-charged glass substrate .…”

“…Earlier works showed that coercivity depended on a favorable orientation of the magnetic nanoplatelets. , To achieve the favorable orientation of the nanoplatelets, various approaches, such as anodic aluminum oxide (AAO) template, electrostatic attraction, and external magnetic field, were used. − For instance, Lukatskaya et al successfully controlled the arrangement of aluminum-doped magnetic strontium hexaferrite nanoplatelets by using the AAO membrane as a template . Kushnir et al prepared strontium hexaferrite nanoplatelets with positive charges and observed a fixed orientation of the nanoplatelets on a negatively surface-charged glass substrate . Such orientation was caused by the electrostatic attraction between the positive charges of the nanoplatelets and the negative charges of the substrate surface, which allowed the large facet of the nanoplatelets to align parallel to the surface of the substrate.…”

Stable colloidal solutions of strontium hexaferrite hard magnetic nanoparticles

“…14 Another interesting effect is the formation of the monolayers of aligned plate-like hexaferrite nanoparticles by electrostatic adsorption. 15 Another very important effect is the magnetic field dependent optical transmission of these colloids. It is related to linear dichroism resulting from unequal absorption of polarized light by colloidal solution for different orientations of an anisotropic particle.…”

“…To demonstrate the processability of the colloids we developed anisotropic arrays of aligned hexaferrite nanorods in anodic alumina channels 14 and particle monolayers on solid substrates. 15 In addition the colloids are ready for common film deposition by electrophoresis or magnetic field gradient. 18,19 Because hexaferrite nanoparticles are well suited for high-density information storage tape systems, 3,20 our stable colloids of well-dispersed high-quality particles could lead to better performance media.…”

Glass-Ceramic Synthesis of Cr-Substituted Strontium Hexaferrite Nanoparticles with Enhanced Coercivity

“…For example, hexaferrites are attractive for high-density magnetic recording tape media [ 1 , 4 , 5 ] and low-frequency magnetic hyperthermia [ 6 ], as well as for magnetic colloids of hard magnetic particles, which are hugely different from traditional magnetite-based ferrofluids and demonstrate several unique properties [ 7 , 8 , 9 ]. Certainly, the colloidal hexafeFrrite nanoparticles are building blocks for the creation of magnetic nanostructures [ 10 , 11 ], nanocomposites [ 12 , 13 ], and various nanomaterials [ 14 , 15 , 16 , 17 , 18 ].…”