arXiv subjects

Rongkun Han

Publications and source records attributed to Rongkun Han.

4 recordsLinked to original sources

arXiv2026

Field-Free Reconfigurable Spin Logic in Compositionally Graded MnxCoAl Layer

Spintronic logic-in-memory provides a route to reducing data-transfer energy consumption and accelerating computation by integrating nonvolatile storage and logic functions within a single physical unit. Here, we investigate field-free spin-orbit-torque (SOT) switching and reconfigurable spin logic in a vertically composition-graded MnxCoAl/Pt heterostructure. In contrast to the uniform-composition Mn1.8CoAl/Pt and Mn2.5CoAl/Pt control devices, the Mn1.8-2.5CoAl gradient device exhibits deterministic SOT switching under zero external magnetic field. Dzyaloshinskii-Moriya interaction (DMI)-related measurements reveal a finite characteristic effective-field scale, indicating the involvement of chiral magnetization-reversal processes. Meanwhile, the vertical composition gradient introduces magnetic inhomogeneity that can modify domain nucleation and propagation, and the combined effects are consistent with the observed field-free switching behavior. The composition-gradient device further exhibits accumulative multistate switching with stable intermediate Hall-resistance states under zero magnetic field, whereas the uniform-composition controls do not show comparable stable multistate behavior. By tailoring the amplitude, polarity, and sequence of current pulses, the device can be tuned between binary and multilevel switching modes, enabling the experimental realization of AND, OR, NAND, and NOR Boolean operations within the same Hall-bar device without any external magnetic field. These results extend Mn-Co-Al Heusler heterostructures from field-assisted SOT switching toward field-free magnetization control, multistate operation, and reconfigurable spin logic through vertical composition engineering.

cond-mat.mes-hall↗

arXiv2026

Symmetry-Dependent Polarity Reversal of Bulk Spin-Orbit Torque in Single-Layer MnCoGa

Controlling the magnitude and polarity of spin-orbit torque (SOT) is essential for manipulating magnetization in spintronic devices. Here, we realize bulk spin-orbit torque (SOT) in a single-layer Mn1.6Co1.4Ga (MCG) Heusler alloy and achieve lattice strain-controlled reversal of SOT polarity. SOT-driven magnetization switching is achieved over a thickness range of 3-20 nm, with the switching polarity reversed between the strongly strained ultrathin regime and thicker films. First-principles calculations reveal a sizable intrinsic spin Hall conductivity (SHC) in MCG originating from its topological band structure, which is enhanced by the tetragonal distortion without changing sign. Together with the thickness-dependent structural evolution, we demonstrate that the reversal of SOT polarity does not originate from a sign change of the SHC, but rather from lattice distortion induced symmetry breaking that modifies the conversion of spin current into a net bulk SOT, thereby controlling its polarity. These results establish strain-controlled structural symmetry as an additional degree of freedom for tuning bulk SOT in magnetic single layers.

cond-mat.mes-hall↗

arXiv2026

Self-induced spin-orbit torque switching in a synthetic antiferromagnetic Co 2 MnGa /MnGa bilayer

The large intrinsic spin current in magnetic Weyl semimetals (WSMs) provides a promising platform for spin-orbit torque (SOT) devices. Here, we demonstrate SOTdriven magnetization switching in a synthetic antiferromagnet (SAF) composed of a Co2MnGa(CMG)/MnGa bilayer. In this heavy metal-free structure, CMG film functions simultaneously as a spin current source and as a magnetic layer. Macrospin simulations confirm the self-induced switching mechanism in the bilayer. The SOT generated by CMG switches the MnGa layer, which in turn triggers the reversal of the CMG layer via strong antiferromagnetic exchange coupling. These results elucidate the spin dynamics in SAFs and provide a new pathway toward SOT devices with selfinduced magnetization switching.

cond-mat.mes-hall↗

arXiv2026

Programmable Asymmetric Spin-Orbit Torque Switching for Spin Logic

Spin logic devices provide a promising route toward ultralow-power and nonvolatile information processing. In this work, we demonstrate field-free spin-orbit torque-induced asymmetric magnetization switching in in-plane anisotropy (IMA) and perpendicular magnetic anisotropy heterostructures, characterized by different critical switching currents under opposite current polarities. Combined experiments and macrospin simulations reveal that the asymmetric switching originates from an in-plane effective field Hy , which breaks the Myz mirror symmetry of the system. By controlling the magnetization direction of the IMA layer, both the switching polarity and bias direction can be tuned. Building on four distinct types of asymmetric switching behaviors, we realize a reconfigurable spin logic operation within a single Hall-bar device. These results clarify the physical origin of asymmetric magnetization switching and demonstrate an approach for realizing reconfigurable spin logic devices.

cond-mat.mes-hall↗