Effects of temperature cycling on domain wall pinning in Py/Gd ferrimagnetic multilayers

Due to their potential applications in high speed, low power spintronic devices, ferrimagnetic domains and domain structures have garnered intense interest in recent years. Of particular interest is the tunable environment of ferrimagnets combined with the interactions between magnetic quasiparticles, such as vortices, and external fields or currents. In our work, we explore the response of microstructured Permalloy (Py)/Gadolinium(Gd) ferrimagnetic multilayers utilizing Kerr microscopy as a function of composition and temperature. As expected, for increasing Gd layer thicknesses beyond the compensation point, the coercivity decreases. Similarly, for Gd-doped films, we observe decreasing coercivity at higher temperatures. Through direct imaging of the magnetic domain structure as a response to the external field, we see that this decrease with temperature results in significantly weaker pinning effects, suggesting a strong influence of the Gd sublattice on pinning in artificial ferrimagnetic multilayers. Through small temperature variations, depinning can be induced without changes to the external magnetic field.