[20a-B101-1~10] 10.3 Spin devices, magnetic memories and storages

▼ [20a-B101-5] TMR properties in MTJs with epitaxial FeAlSi free layer

〇(DC)Shoma Akamatsu¹, Takafumi Nakano¹, Masakiyo Tsunoda¹, Yasuo Ando¹, Mikihiko Oogane¹ (1.Tohoku Univ.)

Keywords:TMR effect, MTJ, Sendust

Ferromagnetic materials with high tunnel magnetoresistance (TMR) ratio and low magnetic anisotropy field are required to improve the performance of TMR sensors based on magnetic tunnel junctions (MTJs). We focused on Sendust alloy (Fe_73.7Al_9.7Si_16.6), which shows good soft magnetic properties in the bulk state. In this study, MTJs using epitaxial FeAlSi films as the free layer were fabricated and their TMR properties were investigated in detail. As a result, a relatively high TMR ratio of 104% (180%) was observed at room temperature (10 K), and the spin polarization of FeAlSi estimated from the TMR ratio at 10 K is 0.58, suggesting that coherent tunneling of spin polarized Δ1 electrons as well as Fe/MgO/Fe- MTJs. The asymmetry of the bias voltage dependence in the MTJs with FeAlSi can be attributed to the different materials used in the upper and lower ferromagnetic layers. The conductance increases from around +0.2 V, indicating that electrons with other than Δ1 symmetry tunneling from the FeAlSi layer contribute to the tunneling. Further detailed investigations, including first-principles calculations, are needed to determine the cause of the bias voltage dependence.