Electrically Tunable Stochastic Devices via Magnetic Fluctuations in V-Doped WSe₂

Fluctuations are ubiquitous in magnetic materials and provoke random telegraph noise (RTN) that can be used for spiking neuron devices, random number generators, probability bits, and neuromorphic computing. Two-dimensional (2D) magnetic materials are thought to possess inherently stronger fluctuations than their three-dimensional (3D) counterparts, which yield weaker fluctuations that are more difficult to control with external forces. This has been demonstrated in 2D van der Waals (vdW) CrBr₃ utilizing the magneto-optic Kerr effect, but electrical measurement of these fluctuations has not yet been demonstrated. Moreover, these fluctuations only appear over a narrow range of transition temperatures centered around 22 K. For practical applications, such magnetic fluctuations in 2D materials should be well-described and electrically tunable across a wide range of temperatures, but there has been limited progress to date on this front. Here, we report magnetic fluctuations in a vdW-layered semiconductor with a magnetic dopant by investigating the giant RTN of resistance across the vertical tunnel junctions of a graphene/V-WSe2/graphene (Gr/V-WSe2/Gr) device. We identify bistable magnetic states from discrete Gaussian peaks of the RTN histogram, which were further confirmed by 1/f₂ features in the noise power spectrum. We detect three fluctuation categories in the resistance change: small changes from the intralayer coupling between magnetic domains at high temperatures, anomalous large resistance changes over a wide range of temperatures, and persistent large resistance changes originating from magnetic interlayer coupling at low temperatures. This device reveals high-amplitude RTN in resistance as large as 40% with a well-defined bistable state that can be tuned by magnetic and electric fields.