Magnetic tunnel junctions (MTJs) are currently at the forefront of spintronics research because their large magnetoresistance (MR) and high sensitivity make them an attractive application prospect for magnetic memories and magnetic sensors 1. MTJs with perpendicular magnetic anisotropy (PMA) are advantageous over in-plane devices due to their scalability, stronger remnant magnetization for a smaller demagnetizing field in the perpendicular direction, and higher signal-to-noise ratio due to the enhanced uniaxial orientation 1. The perpendicular anisotropy is also essential to achieve faster magnetization switching and to minimize stray fields from a magnetoresistance junction. Heusler compounds are one of the most promising candidates for MTJ electrodes because their half-metallic states can help achieve 100 % spin polarization at room temperature, leading to an infinite magnetoresistance ratio. Furthermore, these materials have additional advantages, including high Curie temperature and long spin diffusion length 2. Recently, our group has discovered Weyl semi-metal behaviors 3, and PMA 4 in Heusler-based Co2MnGa ultrathin films, making it a promising material for exploring spin-polarising devices. In this work, we used Co2MnGa electrodes to obtain perpendicularly magnetized MTJ stacks. We used thin-film sputtering and photolithography to fabricate the devices. We optimized the devices by precisely varying the thickness of each Co2MnGa and MgO layer and annealing conditions. We used the magneto-optical Kerr effect (MOKE) microscopy for domain imaging and MR measurements of the multilayer stacks. The MTJ showed strong PMA, and we could identify two distinct magnetic steps in the field sweep curve corresponding to the switching direction of the two magnetic layers. The devices also showed high MR, demonstrating that Co2MnGa-based perpendicular MTJs are a strong candidate for the next generation of spintronic devices. References 1 Maciel, N.; Marques, E.; Naviner, L.; Zhou, Y.; Cai, H. Magnetic Tunnel Junction Applications. Sensors, 2019, 20 (1), 121. https://doi.org/10.3390/s20010121.

2 Elphick, K.; Frost, W.; Samiepour, M.; Kubota, T.; Takanashi, K.; Sukegawa, H.; Mitani, S.; Hirohata, A. Heusler alloys for spintronic devices: review on recent development and future perspectives. Sci. Technol. Adv. Mater., 2021, 22 (1), 235–271. https://doi.org/10.1080/14686996.2020.1812364. 3 Zhang, Y.; Yin, Y.; Dubuis, G.; Butler, T.; Medhekar, N. V.; Granville, S. Berry curvature origin of the thickness-dependent anomalous Hall effect in a ferromagnetic Weyl semi-metal. npj Quantum Mater., 2021, 6 (1). https://doi.org/10.1038/s41535-021-00315-8. 4 Ludbrook, B. M.; Ruck, B. J.; Granville, S. Perpendicular magnetic anisotropy in Co 2 MnGa and its anomalous Hall effect. Appl. Phys. Lett., 2017, 110 (6), 062408. https://doi.org/10.1063/1.4976078.