Kumar Deepak, Ishibashi Mio, Roy Tufan, Tsujikawa Masahito, Shirai Masafumi, Mizukami Shigemi
WPI Advanced Institute for Materials Research, Tohoku University, Sendai, Japan.
Center for Science and Innovation in Spintronics, Tohoku University, Sendai, Japan.
Sci Technol Adv Mater. 2024 Nov 13;25(1):2421746. doi: 10.1080/14686996.2024.2421746. eCollection 2024.
A body-centered cubic (bcc) FeCo(B) is a current standard magnetic material for perpendicular magnetic tunnel junctions (-MTJs) showing both large tunnel magnetoresistance (TMR) and high interfacial perpendicular magnetic anisotropy (PMA) when MgO is utilized as a barrier material of -MTJs. Since the -MTJ is a key device of current spintronics memory, . spin-transfer-torque magnetoresistive random access memory (STT-MRAM), it attracts attention for further advance to explore new magnetic materials showing both large PMA and TMR. However, there have been no such materials other than FeCo(B)/MgO. Here, we report, for the first time, PMA in metastable bcc Co-based alloy, . bcc CoMnFe thin films which are known to exhibit large TMR effect when used for electrodes of MTJs with the MgO barrier. The largest intrinsic PMAs were about 0.6 and 0.8 MJ/m in a few nanometer-thick CoMnFe alloy film and multilayer film, respectively. Our calculation suggested that PMA originates from tetragonal strain and the value exceeds 1 MJ/m with optimizing strain and alloys composition. The simulation of the thermal stability factor indicates that the magnetic properties obtained satisfy the requirement of the data retention performance of -1 nm STT-MRAM. The large PMA and high TMR effect in bcc CoMnFe/MgO, which were rarely observed in materials other than FeCo(B)/MgO, indicate that bcc CoMnFe/MgO is one of the potential candidates of the materials for -1 nm STT-MRAM.
体心立方（bcc）FeCo（B）是目前用于垂直磁隧道结（-MTJs）的标准磁性材料，当氧化镁用作-MTJs的势垒材料时，它既表现出大的隧道磁电阻（TMR）又具有高的界面垂直磁各向异性（PMA）。由于-MTJ是当前自旋电子学存储器的关键器件，即自旋转移矩磁阻随机存取存储器（STT-MRAM），因此探索兼具大PMA和TMR的新型磁性材料以实现进一步发展备受关注。然而，除了FeCo（B）/MgO之外，尚无此类材料。在此，我们首次报道了亚稳态bcc钴基合金中的PMA，即bcc CoMnFe薄膜，当将其用作具有MgO势垒的MTJs电极时，已知其会表现出大的TMR效应。在几纳米厚的CoMnFe合金薄膜和多层薄膜中，最大本征PMA分别约为0.6和0.8 MJ/m²。我们的计算表明，PMA源自四方应变，通过优化应变和合金成分，该值可超过1 MJ/m²。热稳定性因子的模拟表明，所获得的磁性能满足-1 nm STT-MRAM数据保持性能的要求。bcc CoMnFe/MgO中罕见的大PMA和高TMR效应（FeCo（B）/MgO以外的材料中很少观察到）表明，bcc CoMnFe/MgO是-1 nm STT-MRAM材料的潜在候选者之一。
