A particle that can be used to create an active magnetic metamaterial has been designed using an FET transistor loaded in its gate by a conducting ring and in its source by a parallel resonance circuit. The design procedure is discussed and the working principle is experimentally demonstrated in the RF range.
@article{arxiv.1106.4144,
title = {An FET-Based Unit Cell for an Active Magnetic Metamaterial},
author = {Lukas Jelinek and Jan Machac},
journal= {arXiv preprint arXiv:1106.4144},
year = {2014}
}