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 An┼żelak
bernarda.anzelak@ijs.si
Telephone: +386 1 477 33 23

Magnetoelectrics

 

Multiferroics are materials that combine two “ferro” properties, i.e., ferroelectricity and ferro/ferrimagnetism. In such materials the magnetic properties can be controlled by external electric fields and the electric properties by external magnetic fields. The possibility of tuning the magnetic properties by external electric fields enables the development of high-frequency components (magnetodielectrics). Their operation could be controlled by an external electric field, which is not possible in conventional magnetic components. Single-phase or so-called intrinsic magento-electric materials are very rare and the coupling of both properties is relatively weak. Therefore, magnetoelectrics are usually prepared as composites, composed of piezoelectric and magnetostrictive materials.

 

The desired control over the structuring of the nanocomposites could be achieved by the deposition of nanoparticles of different compositions from colloidal suspensions under the influence of external electric or magnetic fields. A two-step procedure was designed. In the first step the structured layer of magnetic material (Co ferrite) is prepared by the deposition of the particles in an external magnetic field. The structuring of the deposited layer is optimized by the control of the suspension properties (e.g., stability, particle size, concentration) and the process conditions (e.g., magnetic field strength and distribution, drying rate, layer thickness). In the second step the empty space is filled by piezoelectric particles, deposited by electrophoresis.  

 

 

Image of the columnar structure, prepared by the deposition of Co ferrite particles in an external magnetic field.

 

The mechanical coupling of the functional properties in composite multiferroics is possible only if the two phases are in close contact. Ceramic composites are usually prepared by the co-sintering of two components. In the case of composite multiferroics, co-sintering is in general impossible because the components chemically react at the sintering temperature. Special approaches are needed to obtain a dense material. For example, by the utilization of nanoparticles the densification temperature can be reduced to such an extent that chemical reactions between the components do not proceed. 

JSI - Synthesis of Materials K8