Size dependence of the properties of synthetic-antiferromagnet-based stochastic magnetic tunnel junctions for probabilistic computing Takuma Kinoshita, Ju-Young Yoon, Nuno Caçoilo, Ryota Mochizuki, Haruna Kaneko, et al. Applied Physics Letters, 2025 Stochastic magnetic tunnel junctions (s-MTJs) are core components for spintronics-based probabilistic computing, offering promising routes toward energy-efficient unconventional computing. A synthetic antiferromagnetic (SAF) free layer configuration has been proposed to enhance the robustness of these devices against external magnetic field disturbance. Here, we systematically investigate the stochastic properties of SAF-based s-MTJs, with a particular focus on their size dependence. We demonstrate that decreasing the junction size from approximately 100 nm to around 40 nm reduces the relaxation time. Importantly, smaller junctions show markedly enhanced robustness against external magnetic fields, achieving susceptibility values below 0.1 mT−1 for sizes under 80 nm. Furthermore, we observe that smaller junctions exhibit enhanced insensitivity to bias voltage, with sensitivity values of around 0.5 V−1 at device sizes of approximately 40 nm, which is 100 times lower than that of conventional s-MTJs. These quantitative results provide clear guidelines for designing robust and scalable s-MTJ devices, essential for advancing spintronic probabilistic computing toward practical implementation.
Electrical coherent driving of chiral antiferromagnet Yutaro Takeuchi, Yuma Sato, Yuta Yamane, Ju-Young Yoon, Yukinori Kanno, et al. Science, 2025 Electric current driving of antiferromagnetic states at radio or higher frequencies remains challenging to achieve. In this study, we report all-electrical, gigahertz-range coherent driving of chiral antiferromagnet manganese-tin (Mn 3 Sn) nanodot samples. High coherence in multiple trials and threshold current insensitive to pulse width, in contrast to results observed with ferromagnets, were achieved in subnanosecond range, allowing 1000/1000 switching by 0.1-nanosecond pulses at zero field. These features are attributed to the inertial nature of antiferromagnetic excitations. Our study highlights the potential of antiferromagnetic spintronics to combine high speed and high efficiency in magnetic device operations.
Magnetic phase diagram of Mn3+xSn1−x epitaxial thin films: Extending the anomalous Hall effect to low temperatures via intrinsic alloying K. Gas, J.-Y. Yoon, Y. Sato, H. Kubota, P. Dłużewski, et al. APL Materials, 2025 Antiferromagnets with broken time-reversal symmetry, such as Mn3Sn, have emerged as promising platforms for exploring topological and correlated electron physics. Mn3Sn is known to show two magnetic phase transitions: a non-collinear inverse triangular antiferromagnetic (IT-AFM) spin configuration is formed below its Néel temperature (TN ≅ 420 K), whereas at T1 that usually locates below room temperature, it transits to an incommensurate spin state. Accordingly, intriguing properties such as a strong anomalous Hall effect, observed from TN to T1, disappear below T1, limiting its utility at low temperatures. While bulk Mn3Sn has been extensively studied, the magnetic phase transitions and their tunability in thin films remain largely unexplored. Here, we investigate the magnetic and magneto-transport properties of Mn3+xSn1−x epitaxial thin films prepared by magnetron sputtering, systematically varying the Mn–Sn composition. Our results reveal that intrinsic alloying with Mn provides us with a handle to tune T1, with the IT-AFM phase stabilized down to liquid helium temperatures for x > 0.15. From a magnetic phase diagram for epitaxial thin films, we also find a consistent magnetic anomaly ∼55 K below TN, accompanied by thermal hysteresis. Furthermore, the reduction in TN in thin films relative to bulk values is shown to correlate with lattice parameter changes. These findings extend the accessible temperature range for Mn3Sn’s topological properties, paving the way for novel applications and further investigations into the interplay of spin, lattice, and electronic degrees of freedom in thin-film geometries.
Thermal stability of non-collinear antiferromagnetic Mn3Sn nanodot Yuma Sato, Yutaro Takeuchi, Yuta Yamane, Ju-Young Yoon, Shun Kanai, et al. Applied Physics Letters, 2023 D019-Mn3Sn, an antiferromagnet having a non-collinear spin structure in a kagome lattice, has attracted great attention owing to various intriguing properties such as large anomalous Hall effect. Stability of a magnetic state against thermal fluctuation, characterized in general by the thermal stability factor Δ, has been well studied in ferromagnetic systems but not for antiferromagnets. Here, we study Δ of the antiferromagnetic Mn3Sn nanodots as a function of their diameter D. To quantify Δ, we measure the switching probability as a function of the pulse-field amplitude and analyze the results based on a model taking account of two and sixfold magnetic anisotropies in the kagome plane. We observe no significant change in Δ down to D = 300 nm below which it decreases with D. The obtained D dependence is well explained by a single-domain and nucleation-mediated reversal models. These findings provide a basis to understand the thermal fluctuation and reversal mechanism of antiferromagnets for device applications.
