Spin-Precession Organic Magnetic Sensor

Abstract

Abstract : The three major tasks we addressed in this project were to: (a) identify the issues for demonstration of a polymer-based spin-precession magnetic sensor; (b) develop theoretical and computational techniques to study the effect of the interface between ferromagnetic metal and polymers for FET applications; and (c) apply the existing light propagation codes to study transmission of 1.5 micron wavelength light through GaAs. We have completed all three tasks, and the major results of our 18-month effort are: (1) Detailed device modeling confirms that a room temperature detectivity of ~ 50 fT/square root of Hz is possible with an appropriately fabricated polymer magnetic sensor. (2) Self-consistent charge and spin transport calculations indicate that doping concentrations and field-dependent mobility in the polymer and Schottky barrier height with the contacts can be optimized for enhanced field effect transistor performance and magnetic sensor sensitivity. (3) La0.7Sr0.3MnO3 (LSMO) is demonstrated to be a ferromagnetic metal at room temperature. (4) Focused ion beam (FIB) lithography has been used to fabricate ultra-narrow trenches required for high-performance magnetic sensors, but the use of Ga+ ions in the FIB oxidizes the ferromagnetic surface and prevents spin or charge injection from half-metal La0.7Sr0.3MnO3 (LSMO). (5) We demonstrated the synthesis of very low mobility but heavily doped polymers and used them in magnetic sensor fabrication. (6) We calculated two-photon and free carrier absorption coefficients and changes to the refractive index used in light propagation codes and concluded that GaInAs alloy is a better limiting material at 1.5 micron than GaAs. This report discusses our results and conclusions on key requirements.