Calculation of Minimum Parameters Required for Low-Field Low-Size Nano Nuclear Magnetic Resonance (NanoNMR)

The objective of this research is to calculate the minimum parameters required to make low-field low-size nano nuclear magnetic resonance (NanoNMR) a viable technology and potentially one of the future lab-on-chip technologies. By low field we signify an externally applied magnetic field of less than 0.5 T, and by low size we mean a magnet whose largest physical dimension does not exceed 25 mm. The goal is to develop small and cost-effective NMR spectrometers that can be used at room temperature in a small office environment. In this paper, tunneling magneto resistance (TMR) devices are used to sense the NMR signal. The parameters that are calculated are: minimum sample size and concentration required to obtain an adequate NMR signal, TMR sensor size, and its distance to the sample, RF coil size, RF frequency, and power. The nanoscale TMR sensors proposed in this paper were designed using an in-house developed software tool. The optimally calculated TMR sensors have Fe₅₀ Co₅₀ PL and FL layers, an area of 100 nm times 100 nm, a 0.3-nm-thick AI₂O₃ barrier and is biased at 200 mV.