Distinct skyrmion phases at room temperature in two-dimensional ferromagnet Fe3GaTe2.

Distinct skyrmion phases at room temperature hosted by one material offer additional degree of freedom for the design of topology-based compact and energetically-efficient spintronic devices. The field has been extended to low-dimensional magnets with the discovery of magnetism in two-dimensional van der Waals magnets. However, creating multiple skyrmion phases in 2D magnets, especially above room temperature, remains a major challenge. Here, we report the experimental observation of mixed-type skyrmions, exhibiting both Bloch and hybrid characteristics, in a room-temperature ferromagnet Fe3GaTe2. Analysis of the magnetic intensities under varied imaging conditions coupled with complementary simulations reveal that spontaneous Bloch skyrmions exist as the magnetic ground state with the coexistence of hybrid stripes domain, on account of the interplay between the dipolar interaction and the Dzyaloshinskii-Moriya interaction. Moreover, hybrid skyrmions are created and their coexisting phases with Bloch skyrmions exhibit considerably high thermostability, enduring up to 328 K. The findings open perspectives for 2D spintronic devices incorporating distinct skyrmion phases at room temperature.

Current-Controllable and Reversible Multi-Resistance-State Based on Domain Wall Number Transition in 2D Ferromagnet Fe3GeTe2.

Controlling the multi-state switching is significantly essential for the extensive utilization of 2D ferromagnet in magnetic racetrack memories, topological devices, and neuromorphic computing devices. The development of all-electric functional nanodevices with multi-state switching and a rapid reset remains challenging. Herein, to imitate the potentiation and depression process of biological synapses, a full-current strategy is unprecedently established by the controllable resistance-state switching originating from the spin configuration rearrangement by domain wall number modulation in Fe3GeTe2. In particular, a strong correlation is uncovered in the reduction of domain wall number with the corresponding resistance decreasing by in-situ Lorentz transmission electron microscopy. Interestingly, the magnetic state is reversed instantly to the multi-domain wall state under a single pulse current with a higher amplitude, attributed to the rapid thermal demagnetization by simulation. Based on the neuromorphic computing system with full-current-driven artificial Fe3GeTe2 synapses with multi-state switching, a high accuracy of ≈91% is achieved in the handwriting image recognition pattern. The results identify 2D ferromagnet as an intriguing candidate for future advanced neuromorphic spintronics.