Periodic Reporting for period 3 - FeMiT (Ferrites-by-design for Millimeter-wave and Terahertz Technologies)
Okres sprawozdawczy: 2022-05-01 do 2023-10-31
The ongoing exponential increase in data traffic threatens with saturating the narrow spectrum of today’s networks. To overcome this issue, the fifth generation of wireless technology (5G) is shifting to higher frequencies, into the mm-waves, where plenty of bandwidth is available. A big challenge of mm-waves is that these only allow line-of sight propagation, making the transition to higher frequencies a real paradigm change, with the communications relying on myriads of closely scattered small antennas. Thus, besides working at tens to hundreds of GHz, the new communication devices will have to be cheap, low power and miniaturized. This will in particular affect the ferrite non-reciprocal devices, such as the circulators which isolate emitting antennas from one another. The ferrites currently used in non-reciprocal wireless components only operate in the first portion of the mm-wave band, using external magnetic fields which makes them bulky, expensive and can only work at one frequency. The key functional property of ferrites in those devices is their ferromagnetic resonance (FMR) by which, at a given frequency, the propagation or absorption of electromagnetic waves through a ferrite depends on their direction with respect to the magnetization. Since the frequency at which the FMR occurs increases with the magnetic anisotropy of the ferrite, very high magnetic anisotropy ferrites are needed for operating at mm-waves.
The overall objective of FeMiT is developing a new family of ferrites based on epsilon-Fe2O3, a material with a high magnetic anisotropy, which can work in non-reciprocal wireless components at higher frequencies without the need of external magnetic fields.
The overall objective of FeMiT is developing a new family of ferrites based on epsilon-Fe2O3, a material with a high magnetic anisotropy, which can work in non-reciprocal wireless components at higher frequencies without the need of external magnetic fields.
The possibilities of developing a family of mm-wave ferrites based in family of ferrites based on epsilon-Fe2O3 have been investigated by synthetizing this type of materials with different metal substitutions. Their magnetic properties have been characterized and we have performed different experiments at large facilities to understand the origin of the large magnetic anisotropy of these ferrites. Some specific compositions have been prepared in the form of epitaxial thin films and we have investigated the potential of controlling the FMR frequency of epsilon-Fe2O3 by means of an applied strain. A lab for characterizing the response of those ferrites to mm-waves has been set up.
We have prepared new epsilon-MxFe2-xO3 materials with M=Cr3+, Mn3+, Al3+, In3+, Sc3+, Ga3+ and characterized their structural and functional properties. We have studied in detail the magnetic relaxation of epsilon-Fe2O3 as a function of crystal size and developed a method for increasing the size of the nanoparticles with batch productions in the order of grams. Epitaxial films with out of plane anisotropy have been obtained which could be useful for developing miniaturized circulators. Next steps will be focused on an extensive characterization of the epsilon-MxFe2-xO3 materials response to mm-waves and in the implementation of demonstrators of non-reciprocal devices based on epsilon-MxFe2-xO3 materials. Moreover, we will increase our efforts in understanding the physics of these oxides an in obtaining them in form of larger micrometric powders or single crystals.