Fig. 2: Evaluation of εr for epitaxial MgO-MTJ with thin MgO tunnel barrier.
From: Dielectric constant of MgO tunnel barrier with epitaxial strain
a–c f dependence of Z’ (gray circles) and Z” (orange circles) for devices with tMgO = 2.2, 2.6, and 3.0 nm. The black lines indicate the fitting curves obtained using Eq. (2). d S dependence of Cp for the epitaxial MgO tunnel barrier with tMgO = 3.0 nm. The red closed squares represent Cp values obtained from the frequency dependence of Z” considering Rs. The open squares represent Cp values obtained from the impedance at 1 MHz, ignoring Rs. e tMgO dependence of εr for epitaxial MgO tunnel barriers with 2.2 ≤ tMgO ≤ 3.0 nm obtained by fitting the f dependence of Z” (blue closed circles) and obtained from the impedance at 1 MHz (open circles). εr of the polycrystalline MgO tunnel barrier with tMgO = 2.2 nm is also represented by the black triangle. f tMgO dependence of Rp (left axis) and RA (right axis) for epitaxial MgO tunnel barriers with 2.2 ≤ tMgO ≤ 3.0 nm.
