Achieving deterministic control of magnetic vortex chirality in nanostructures is a critical challenge for advancing next-generation spintronic devices. While spin-polarized currents are widely used to manipulate magnetic states, the role of the accompanying Oersted field is often neglected, as it is generally considered much weaker than the spin-transfer torque. However, in systems with chiral energy degeneracy, such as magnetic vortices, the Oersted field plays an essential role by breaking this degeneracy due to its direction determined by the right-hand rule. In this work, through systematic micromagnetic simulations, we demonstrate that the Oersted field, in combination with tailored pulsed spin-polarized currents, enables deterministic control over both the circulation and polarity of magnetic vortices in geometrically symmetric nanodisks without introducing structural asymmetry.
We first investigate the effect of a Gaussian current pulse with the fixed-layer magnetization along the out-of-plane (+z) direction. The results show that the Oersted field dictates the final vortex circulation, which consistently aligns with its counterclockwise direction. By constructing phase diagrams of the peak current density J₀ versus pulse width σ, we identify the threshold conditions for circulation control and the parameter window for deterministic polarity manipulation. When the current density is too low, the original vortex structure remains intact. When the current density is excessively high with an insuffcient pulse width (σ), the polarity becomes random due to intense precessional dynamics induced by abrupt pulse termination. Only within an appropriate range of J₀ and σ can both circulation and polarity be simultaneously controlled. With the fixed-layer magnetization along +z, the final vortex polarity is consistently upward, owing to the out-of-plane magnetic guidance.
We further examine the case where the fixed-layer magnetization is oriented in-plane (+x). The Oersted field still enforces counterclockwise circulation regardless of the initial vortex state, confirming that circulation control is independent of the fixed-layer orientation. However, polarity control is lost in this configuration, highlighting that deterministic polarity manipulation requires out-of-plane magnetic guidance from the fixed layer.
The influence of nanodisk size on the control thresholds is also systematically studied. For smaller nanodisks (300 nm in diameter), a higher current density (J₀ ≥ 5 × 10¹¹ A/m²) is required to destroy the initial vortex structure, but the polarity is more stable due to fewer vortex-antivortex pairs generated during the transition. For larger nanodisks (800 nm in diameter), a lower current density (J₀ ≥ 2 × 10¹¹ A/m²) is suffcient to reverse the circulation, while an intermediate state where circulation is reversed but polarity remains unchanged is observed, further demonstrating the distinct roles of the Oersted field and spin-transfer torque in circulation and polarity control, respectively.
These results clarify the complementary roles of spin-polarized currents and Oersted fields: the Oersted field governs vortex circulation by breaking chiral energy degeneracy, while the fixed-layer magnetization direction guides polarity selection. By optimizing the current pulse profile, we achieve reliable and simultaneous control of magnetic vortex chirality and polarity without relying on geometric symmetry breaking. This work provides a comprehensive understanding of current-induced magnetic vortex manipulation and offers a practical strategy for developing high-density, low-power spintronic devices based on magnetic vortices.