Tunneling magnetoresistance in MnRuGa based Magnetic Tunnel Junctions


Tunneling magnetoresistance in MnRuGa based Magnetic Tunnel Junctions

Titova, A.; Fowley, C.; Borisov, K.; Betto, D.; Lau, Y. C.; Thiyagarajah, N.; Atcheson, G.; Coey, M.; Stamenov, P.; Rode, K.; Lindner, J.; Fassbender, J.; Deac, A. M.

Abstract

Nowadays great attention has been paid to the research of intermetallic Heusler compounds. These materials have widely tunable properties. They display high spin polarisation [1], low magnetic moment [2] and low Gilbert damping ╬▒ [3]. Furthermore, these thin-film samples can possess huge uniaxial anisotropy fields, exceeding tens of Teslas [4]. Such a wide range of almost completely tunable properties make these materials very attractive for THz based spin-transfer-torque oscillators [6]. Here we have successfully integrated a compensated half-metallic ferrimagnet as a fixed layer in magnetic tunnel junctions (MTJ). Theoretically, this class of materials was predicted in 1995 by van Leuken and de Groot [7], but experimentally the zero-moment half-metal was realized only in 2014 [8] for a near-cubic Heusler alloy of Mn, Ru, and Ga (MRG). We showed that Tunneling Magnetoresistance (TMR) ratio reaches 40% in our stacks. We also demonstrate that the TMR exists even when the net magnetization of MRG is strictly zero, implying that, at compensation, MRG exhibits a sizable spin polarization [9]. We investigated the role of different diffusion barrier layers between MRG and the tunneling barrier as well as annealing temperature.

Keywords: Ferrimagnetism; Half-metals; Magnetic Tunnel Junctions; Heusler Alloy

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