Perpendicularly magnetized ferrimagnetic [Mn50Ga50/Co2FeAl] superlattice and the utilization in magnetic tunnel junctions

Abstract

The ferrimagnetic superlattice (SL) [MnGa/Co2FeAl]n exhibiting perpendicular magnetic anisotropy opened a new method for spintronics materials used in magnetic random access memory, because of the high anisotropy, small damping constant and tunable magnetization. In this work, we fabricated SLs with different MnGa composition and studied the MnGa composition dependence of the structure and magnetic properties of the SLs. Furthermore, we fabricated fully perpendicular magnetic tunnel junctions with SLs as both top and bottom electrodes. A clear tunnel magnetoresistance (TMR) effect with TMR ratio of 1.3% at room temperature was observed.

Perpendicularly Magnetized MnxGa‐Based Magnetic Tunnel Junctions: Materials, Mechanisms, Performances, and Potential Applications

“…Inspired by the artificial AFM formed by superlattice structure, such as [Co/Pt] n and [Co/Pd] n , [100][101][102] Ma et al further investigated the FIM [MnGa/Co 2 FeAl] n superlattice-based pMTJs. [103] Figure 8g plots the typical out-of-plane M-H loops of [Mn 50 Ga 50 (t MnGa nm)/CFA(1.5 nm)] 5 superlattices. A squareshaped hysteresis loop was observed for superlattices with t MnGa ≥ 3.0 nm, indicating that the PMA of these superlattices is originated from MnGa sublayer.…”

“…Notably, the MTJs with the pure Co interlayer exhibit a TMR ratio of 70 (145)% at 300 (10) K. The TMR ratio increases up to 85% (209%) at 300 (10) K with Co 80 Mn 20 interlayer, much higher than all the previous results of Mn x Ga-based MTJs. [82][83][84][86][87][88][103][104][105][106][107] The significant enhancement in the TMRs can be attributed to the electronic band with the Δ1 symmetry of the bcc-CoMn alloy. In addition, the utilization of CoMn interlayer supports the growth of high-quality MgO barrier for sustaining the coherency of the tunnel electrons from the Bloch state in the FM electrodes.…”

“…Moreover, TMR ratio was calculated to be 10% at 300 K and 65% at 10 K, much higher than that of the pMTJ with Co 2 FeAl interlayer. [93,103] In the above-mentioned research, the thickness of bottom Mn x Ga electrodes is typically larger than 20 nm. However, ultrathin magnetic free layer is crucial for pursuing all-electrical operation of MTJ devices by the STT or SOT effect.…”

“…In previous study on FIM [MnGa/Co 2 FeAl] 5 superlattices with tunable compensated magnetic moments, it has been found that H c can be infinite near compensational points. [103,126] To further enhance the dynamic range, an MTJ-based magnetic sensor based on artificial FIM [Mn 2.9 Ga/Co 2 MnSi] n superlattices with large PMA was proposed by Lu et al in 2017. [127] Similar to [MnGa/Co 2 FeAl] 5 superlattice, the compensation temperature can be easily tuned by the thickness ratio.…”

“…i,g) Out-of-plane M-H and R-H loops of pMTJs with core structure of [Mn 50 Ga 50 (6.0 nm)/ CFA(1.5 nm)] 5 /CFA(2.0 nm)/MgO(2.0 nm)/CFA(2.0 nm)/[Mn 50 Ga50 (2 nm)/CFA (1.5 nm)] 5 . Adapted with permission [103]. Copyright 2015, AIP Publishing.…”