MgGa2O4 as alternative barrier for perpendicular MRAM junctions and VCMA

Abstract

The CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) is the central element of any high performance perpendicular Magnetoresistive Random Access Memory (MRAM) device. The MgO tunnel barrier, in contact with CoFeB films at both sides in the magnetic tunnel junction, provides a high tunnel magneto resistance (TMR) and perpendicular magnetic anisotropy (PMA) thanks to the high crystalline quality of the MgO/CoFeB interface achieved upon post-deposition annealing. We study MgGa2O4 as an alternative barrier material due to its lower bandgap and show how to introduce it into state-of-the-art perpendicular MRAM stacks. We demonstrate that thin MgO films at both sides of the barrier are key to ensure a proper crystallization and induce reference layer and free layer perpendicular magnetic anisotropy. Consequently, a stack incorporating a MgGaxOy barrier with full PMA and TMR > 100% can be fabricated with a resistance-area (RA) product as low as 50 Ω μm2, which is of strong interest as a potential barrier in the field of voltage control magnetic anisotropy MRAM.

Giant unilateral electric-field control of magnetic anisotropy in MgO/Rh2CoSb heterojunctions

“…1,23 Exploring large PMA magnetic heterostructures with large VCMA effect is one of the main goals in the development of this new MRAM device. [24][25][26][27][28][29][30][31] The VCMA effect can be evaluated by the VCMA coefficient. In the linear regime, the correlation between VCMA and electric field can be represented by an equation, 15,23,24 VCMA = bE I = bE ext /e > , where b is the VCMA coefficient, E ext is the external electric field, E I is the electric field inside the insulator, and e > is the out-of-plane dielectric constant of the insulator.…”

“…1,23 Exploring large PMA magnetic heterostructures with large VCMA effect is one of the main goals in the development of this new MRAM device. 24–31…”

Perpendicular magnetic anisotropy of Pd/Co2 MnSi/NiFe2O4/Pd multilayers on F-mica substrates

“…[14][15][16] Moreover, spinel oxides, such as MgAl 2 O 4 and MgGa 2 O 4 , can further improve the performance of MTJs when used as a tunnel barrier due to their small lattice mismatch with typical FM electrodes. [17,18] NiFe 2 O 4 (NFO) is a typical ferromagnetic spinel oxide with high magnetic ordering temperature and high saturation susceptibility. It is a very attractive candidate material for spintronic devices.…”

Strain driven phase transition and mechanism for Fe/Ir(111) films

“…Iron and iron-based alloys are the most important materials used in magnetic devices, such as magnetic tunnel junction 26 – 28 , magnetic random access memory 29 , 30 and magnetic sensors 31 – 33 . Because of their different lattice structures, Fe/Ir interfaces function as a platform for controlling pseudomorphic growth, nanostructure evolution, and the formation of strained clusters.…”