Evaluating Epsilon Iron Oxide for Radio Frequency Pulse Generation

Project Overview

This project leveraged Lawrence Livermore National Laboratory's material synthesis capabilities and magnetic material knowledge to evaluate techniques to reduce the ferromagnetic resonance (FMR) frequency of epsilon iron oxide. The FMR frequency was reduced by introducing dopants and modifying critical synthesis parameters such as annealing temperature and anneal time. We evaluated the resultant magnetic properties by measuring the magnetization versus magnetic field as well as airline measurements for determining the high-frequency material properties, both of which are essential for understanding the materials performance in various radio frequency (RF) devices.

During the project, we showed that we can control the crystalline anisotropy of the material depending on the synthesis condition resulting in a decrease in the FMR frequency from 100 GHz down to about 40 GHz. However, detailed material properties at high frequency proved difficult to determine due to excitation of multiple modes inside our airlines. The saturation magnetization was measured to be around 3-4 emu/g. The addition of dopants also increased the percentage of polymorphs (i.e., gamma iron oxide) in the samples to a non-negligible amount and future studies should be done to reduce their presence. Additionally, we developed a simulation tool to predict device performance based on measured results.

Mission Impact

This research impacts Lawrence Livermore National Laboratory's Integrated Deterrence and Technology Competition Mission Focus Area and the Accelerated Materials and Manufacturing Core Competency. This project builds upon the Lab's material synthesis capabilities and the results were used to procure additional LDRD funding to continue to develop and understand novel magnetic materials. Additionally, this research is relevant to other U.S. Government agencies.

Publications, Presentations, and Patents

GYROMAGNETIC NONLINEAR TRANSMISSION LINE FOR RADIO FREQUENCY SIGNAL GENERATION AND PULSE COMPRESSION. J.D. Schneider, A.A. Baker, J Han, L.F. Voss. US Patent App. 17/556,575, 2023