Magnetically tunable nano-superlattice metaconductors for RF applications

A nanomachined ferromagnetic and non-ferromagnetic superlattice approach is used for tunable radio frequency (RF) conductors, where the current flow profile through the volume of the conductor is magnetically manipulated and so is the RF resistance. The magnetically tunable nano-superlattice conductors with a variable ohmic resistance in GHz range are successfully demonstrated. The realized superlattice conductor consists of an alternating 20 layers of Cu/Ni and Cu/NiFe thin films with a thickness of each pair of 150 nm/25 nm where 150 nm is a few times smaller than the skin depth of Cu in the frequency range of interest. As a total multi-layer conductor's thickness of 1.75 μm has shown to have a reverse RF resistance performance as a function of frequency compared to its solid Cu counterpart with the same thickness, we call this artificial conductor as the “metaconductor”. In 10 MHz - 20 GHz frequency range, the metaconductors show an increased ohmic resistance in less than 10 GHz, but a reduced ohmic resistance in greater than 10 GHz range as “low loss conductors” in especially Ku and K bands. The RF frequency showing maximum resistance is magnetically tunable by more than 700 % (1 GHz ~ 7 GHz).

I. Introduction

With the recent technology developments and the emerging internet-of-things (IoT) concept, multiple integrated wireless/access solutions will serve to enable a long-term networked society. Radio frequency (RF) passives including inductors, capacitors, resonators, transmission lines, and antennas are essential parts of such a comprehensive RF system comprising integrated/off-chip components which are required for input/output impedance matching networks, feedings, and overall RF communication. Passive components with lower loss, smaller dimensions and tuning capabilities are highly demanded.