The tunneling magnetoresistance current dependence on cross sectional area, angle and temperature

Abstract

The magnetoresistance of a MgO-based magnetic tunnel junction (MTJ) was studied experimentally. The magnetoresistance as a function of current was measured systematically on MTJs for various MgO cross sectional areas and at various temperatures from 7.5 to 290.1 K. The resistance current dependence of the MTJ was also measured for different angles between the two ferromagnetic layers. By considering particle and angular momentum conservation of transport electrons, the current dependence of magnetoresistance can be explained by the changing of spin polarization in the free magnetic layer of the MTJ. The changing of spin polarization is related to the magnetoresistance, its angular dependence and the threshold current where TMR ratio equals zero. A phenomenological model is used which avoid the complicated barrier details and also describes the data.

Cross-Sectional Area Dependence of Tunnel Magnetoresistance, Thermal Stability, and Critical Current Density in MTJ

“…Thus, while downscaling the lateral dimensions of MTJ device, we predict that dephasing will be a challenge. For higher diameters we can see that the TMR is gradually saturating to a minimum, because for same transverse cut off ratio of numbers of up and down channels remains same but difference in net current carried by these channels in P and AP states is reduced which limits the TMR to a saturating value also shown in [6] [7]. Further, to study the effect of TMR sensitivity on interface quality in terms of disorder such as roughness and bonding at the interface, we varied the onsite potential corresponding to interface layer atoms, and asymmetric variation of TMR is observed.…”

“…Here, dephasing coefficient matrix (D) is chosen according to nature of dephasing for momentum relaxation type D=D0 i,j [30], specifying the correlation between the neighboring random atomic potential at the site 'i' and 'j' ∝ ⟨ * ⟩, while G(E) is the Green's function and ( ) is the electron correlation function. The effect of magnitude of dephasing at a fixed diameter has been studied by [6]. We further extend these studies to analyze the effect of dephasing with scaling of MTJ croo-sectional dimensions.…”

“…Here, k and n correspond to unit cells in x direction, (ɛ0+4t) is the onsite energy, -t models the hopping of an electron from k to k-1 and k+1. ℎ 01 ( , ) = { − , when k = n 0, otherwise }, ℎ 10 = ℎ 01 + (6) We compute the respective eigen states of HT which act as transverse modes, thus conduction band minima for our computation of different charges and spin currents.…”

“…This is particularly true for Fe/MgO based systems due to the symmetry filtering property [5]. Quantization effects in the transverse plane result in a decrease of TMR with an increase in dimensions, and normally around 50 nm, this value starts to saturate to a minimum [6], [7]. The other important metric used in MTJ performance characterization is its thermal stability which determines data retention, read disturbance, memory size, and operating temperature of the STT-RAM [4].…”