Pulsed or Microwave Currents Induced Random Telegraph Signal in a Magnetic Tunnel Junction*

Recent work has shown creation and dynamics of magnetic skyrmions, without the Dzyaloshinskii-Moriya interaction, in the free layer of a magnetic tunnel junction (MTJ) at a temperature of 4K [1]. In order to study how skyrmions, the topological excitations, can be protected against disorders and temperature fluctuations, we have extended our experimental investigation to higher temperatures, up to 200K, for various device sizes. For the intermediate resistance state, initiated by pulse or microwave currents, we have observed stochastic switching between two resistance states, commonly referred as the random telegraph signal (RTS). Statistics of the observed RTS depends on device temperature and microwave stimulation while the corresponding relations have been studied. In conjunction with micro-magnetic simulations, we discuss the interplay of the topological skyrmion and disorder-induced domains in MTJs.

[1] N. E. Penthorn, X. Hao, Z. Wang, Y. Huai, and H.W. Jiang, Experimental Observation of Single Skyrmion Signatures in a Magnetic Tunnel Junction, Phys. Rev. Lett., 122, 257201 (2019).