College of Science & Engineering
This group performs calculations of magnetic properties useful for applications, particularly Spin-Torque RAM (ST-RAM) and magnetic recording. They are using MSI resources for two purposes: finite difference time domain (FDTD) simulations of light propagation from a near field transducer, as used for heat-assisted magnetic recording (HAMR), and micromagnetic calculations of magnetic damping, which is important for microwave devices.
During 2019, the group focused their damping research on 3- and 4-magnon scattering contributions. They are particularly interested in predictions that describe the potential for suppressing large microwave powers while retaining small signals, as used in Frequency Selective Limiters and Signal to Noise Enhancers. They also intend to further develop their study of transients that occur at initial exposure, and which are currently poorly understood. These calculations are particularly time-consuming owing to the presence of two important time scales: 50 fS for the micromagnetic integration vs. 1/GHz for the incident microwave fields. Last year’s results were published in IEEE Transactions on Microwave theory and Techniques, the most prestigious journal in this field, with a second paper under review.
Previously, the group used the FDTD calculations to quantitatively predict the effects of average grain radius, grain boundary thickness, grain size distribution, and other relevant structural parameters on variation of heat absorption from near field spot illumination. Results were published in Physical Review B and IEEE Transactions on Magnetics. In 2020, they intend to examine the effects of surface roughness and distance between near-field transducer and recording media.
In both cases, the researchers calculate the simple (or lower resolution cases) on their workstations, but need the resources of MSI for calculations requiring more memory. For example, their group-owned GPUs have limited memory that is sometimes insufficient for our higher resolution FDTD calculations. The impact of the work will be better optical designs for near field transducers and media, and better rejection of high amplitude microwave signals.