High-Density Physical Random Number Generator Using Spin Signals in Multidomain Ferromagnetic Layer

Figure 1

Multidomain properties of fabricated STT-MRAM cell. (a) MR characteristics of the pMTJ measured in air with perpendicular magnetic fields swept between −2000 and 2000 Oe, at a sample bias voltage of 50 mV. AP-to-P reversal in spin arrangement of two ferromagnetic layers is shown at the point of −580 Oe; P-to-AP reversal is shown ranging from 500 to 1700 Oe. (Inset) SEM image of individual pMTJ nanopillar with 30-nm junction. (b) High resolution transmission electron microscopy (HR-TEM) image of the pMTJ after ion milling. Brightness difference of sidewall of pinned and free layer (PL and FL) shows formation of multidomain ferromagnetic layers and damage from fabrication process, lithography, and ion milling.