Supposedly Hexaferrite (barium ferrite) works at such frequencies. But I have found information that it has permeability = 1.1, so it is not much gently speaking. If there are such high-frequency ferrites with decent permeabilities, where can I buy them?
Seems they aren't economical to mass produce otherwise they would likely be found in all the major cellphones, laptops and other devices which make use of wifi and similar RF bands. Log periodics seem the simplest way to broadband reception.