JSI - Synthesis of Materials K8

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Head of Department 

Prof. Dr. Darko Makovec
darko.makovec@ijs.si 
Telephone: +386 1 477 35 79

 

 

Secretary

Bernarda Anželak
bernarda.anzelak@ijs.si
Telephone: +386 1 477 33 23

Magnetic materials for high-frequency applications – thick films

 

Hexaferrites are materials that are suitable for micro- and mm-wave applications. A common feature of all the structural types is the anisotropic hexagonal structure with anisotropic magnetic properties that enable their application in the remnant state in the absence of an external magnetic field. Because of its simple chemical and crystal structure the BaFe12O19 is the most suitable for the preparation of passive magnetic components. We have developed deposition methods in electric or magnetic fields for thepreparation of oriented BaFe12O19 thick films. The influence of the interparticle forces and the forces acting on the particles on the thick films’ orientation was explained. In the framework of the international project FERFIT we have developed the method and thick films that are 95% magnetically oriented.

 

High-quality thick films can only be prepared from stable suspensions of particles. The thin BaFe12O19 platelets, synthesized by the hydrothermal method, were electro-steric stabilized by dodecylbenzenesulphonic acid and dispersed in 1-buthanol: a schematic representation of the various interactions between two particles (left) and the total interaction energy between two particles of BaFe12O19 (right – each curve represents a different particle size).

 

In the external magnetic field the BaFe12O19 platelets orient perpendicular to the field direction when their magnetization axis lies parallel to the field (left). Because of the interparticle magnetic interactions they preferentially deposit in columns (upper right). A homogeneous thick film can be prepared from stabile suspensions (lower left).

 

The preferential orientation of the thick films can be further enhanced during sintering (left – increased magnetic anisotropy of sintered films relative to the as deposited). Because of the substrate the grain growth is anomalous and directed. Larger grains that are oriented parallel to the substrate grow at the expense of the smaller ones (right).    

JSI - Synthesis of Materials K8