Our company is also targeting higher frequency, higher efficiency range in toroid cores for power switching and sensing!
We have cores that can manage current up to 700-800 A keeping relative permeability very independently from excitation and frequency as well up to the MHz range, which is idle for AC sensing:
Of course the Power loss density is excitation dependent, but very much independent from frequency if we stay below 300mT excitation and 500kHz. Currently we can only measure the losses including all the electronics so it could be even better with optimized power electronics.
We are testing our cores with GaN high efficient switching to our current limits
Since we would like to concentrate on developing these cores tailored to your custom needs, we are looking for partners, who would be able to stress these cores to the limits and give us feedback to optimize them to the specific applications.