As one of the next-generation memory technologies, magnetic random access memory (MRAM) is of great interest because of its non-volatility, high access speed, large integration density and low power consumption. Current-induced spin-orbit torque (SOT) magnetization switching has been proposed for improving the writing performance of MRAM. Meanwhile, it has been demonstrated that the Co-based full Heusler alloys show potential for increasing the magnetoresistance ratio and achieving efficient reading due to their relatively large spin polarization1. Therefore, achieving the SOT magnetization switching in full Huesler alloys will be promising for optimizing both the reading and writing performance of MRAM devices. Here, we report a successful full SOT magnetization switching in a perpendicularly magnetized full Heusler alloy Co2FeSi2 by using Pd as a spin current generating layer. To eliminate the heating effect, a large writing pulse current with a pulse width of 0.1 ms (red columns in Fig. 1) was applied to switch the magnetization, and a small reading current of 1 mA (blue columns in Fig. 1) was applied for 0.5 s to read the Hall resistance. As shown in Fig. 2, with the assistance of the external magnetic field of 500 Oe, the magnetization can be fully switched with a switching current density of 3.7×107 A cm-2, which is in the same order of magnitude as that required in the conventional heavy metal (HM)/ferromagnet system even though the Pd shows a relatively smaller spin Hall angle than that of HM3. By using harmonic Hall measurements, the damping-like and field-like effective fields per unit current density are estimated to be 56.9 (10–7 Oe A–1 cm2) and 39.8 (10–7 Oe A–1 cm2), respectively. Our findings will advance the development of SOT-MRAM devices with both better reading and writing performance. This work was partly supported by Grants-in-Aid for Scientific Research (Nos. 18H03860, 20H05650, and 20F20366), CREST Program of JST (JPMJCR1777), Spintronics Research Network of Japan (Spin-RNJ), and Grant-in-Aid for JSPS Fellows (20F20366).

![](https://assets.underline.io/uploads/markdown_image/1/image/3b1aaee3c5eb41883e2f839f28df7ddf.jpg)


Fig. 1 Pulse current train used for the SOT switching measurements.

![](https://assets.underline.io/uploads/markdown_image/1/image/2dd84c170180b84b3de155838d52a263.jpg)

Fig. 2 SOT switching in the MgO/Co2FeSi/Pd heterostructure at room temperature.

Spin-orbit torque magnetization switching in a perpendicularly magnetized full Heusler alloy Co2FeSi

Material structures containing tetrahedral FeAs bonds, depending on their density and geometrical distribution, can host several competing quantum ground states ranging from superconductivity to ferromagnetism. In Fe-based superconductors where the FeAs bonds are confined in 2D monolayers (MLs), the magnetic ground state of the Fe spins is antiferromagnetic1. On the other hand, in Fe-based ferromagnetic semiconductors such as (In,Fe)As where the FeAs bonds are distributed randomly in a three-dimensional (3D) InAs matrix, the Fe spins are coupled ferromagnetically via interactions with electron carriers2. Here we examine structures of quasi two-dimensional (2D) layers of tetrahedral FeAs bonds embedded with a regular interval in a semiconductor InAs matrix, which resemble the crystal structure of Fe-based superconductors. The samples were grown by low-temperature molecular beam epitaxy on InAs (001) or semi-insulating GaAs (001) substrates. Lattice images by scanning transmission electron microscopy (STEM) reveal that the zinc-blende structure of the host InAs is well maintained, and the Fe atoms are mainly confined within a thickness of 2-3 MLs (Fig. 1a). We study magnetic and transport properties of a series of FeAs/InAs superlattices (thickness is fixed at 12 nm) containing (1ML of FeAs / t ML of InAs) x N periods (t = 20, 10, 7, 5; N = 1, 3, 5, 7) (the inset of Fig. 1(b)). All the samples exhibit intrinsic ferromagnetism, and the TC value changes rapidly as t-3 (Fig 1b). Furthermore, extremely large magnetoresistance (MR) (~500%, Fig. 1c) are observed, whose origin can be attributed to the giant MR occurring in these multilayer structures. These interesting features indicate that the FeAs/InAs superlattice structures are promising for functional spintronic devices3. This work was partly supported by Grants-in-Aid for Scientific Research (17H04922, 18H05345, 19H05602, 19K21961), CREST program (JPMJCR1777) and PRESTO program (JPMJPR19LB) of JST, and Spin-RNJ.References: [1] H. Hosono et al. Materials Today 21, 278-302 (2018). [2] P. N. Hai, L. D. Anh et al., Appl. Phys. Lett. 101, 182403 (2012). [3] L. D. Anh et al, ArXiv:2005.10181 (2020).

Ferromagnetism and giant magnetoresistance in zinc-blende FeAs/InAs superlattice structures

**Session chair:** Denys Makarov, Helmholtz-Zentrum Dresden-Rossendorf


GOL - MRAM, Magnetic Logic and Related Devices II

technical paper

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O1: 2D Magnetic Materials

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Le Duc Anh

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Spin-orbit torque magnetization switching in a perpendicularly magnetized full Heusler alloy Co2FeSi

Ferromagnetism and giant magnetoresistance in zinc-blende FeAs/InAs superlattice structures

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