Ultrafast domain wall motion in ferrimagnets induced by magnetic anisotropy gradient

Abstract

The ultrafast magnetic dynamics in compensated ferrimagnets not only provides information similar to antiferromagnetic dynamics, but more importantly opens new opportunities for future spintronic devices [Kim et al., Nat. Mater. 16, 1187]. One of the most essential issues for device design is searching for low-power-consuming and high-efficient methods of controlling domain wall. In this work, we propose to use the voltage-controlled magnetic anisotropy gradient as an excitation source to drive the domain wall motion in ferrimagnets. The ultrafast wall motion under the anisotropy gradient is predicted theoretically based on the collective coordinate theory, which is also confirmed by the atomistic micromagnetic simulations. The antiferromagnetic spin dynamics is realized at the angular momentum compensation point, and the wall shifting has a constant speed under small gradient and can be slightly accelerated under large gradient due to the broadened wall width during the motion. For nonzero net angular momentum, the Walker breakdown occurs at a critical anisotropy gradient significantly depending on the second anisotropy and interfacial Dzyaloshinkii-Moriya interaction, which is highly appreciated for further experiments including the materials selection and device geometry design. More importantly, this work unveils a low-power-consuming and high-efficient method of controlling the domain wall in ferrimagnets, benefiting to future spintronic applications.

Strain-induced domain wall motion in ferrimagnetic nanowire

“…As a matter of fact, earlier works have reported ultrafast domain wall dynamics in ferrimagnets driven by various stimuli including electrical current [15,16], magnetic field [17][18][19], and magnetic anisotropy gradient [20]. For example, a domain wall speed up to ∼20 km s −1 T −1 has been reported experimentally in the vicinity of T A in the rareearth 3d transition-metal ferrimagnets [1], confirming again the significant potential of ferrimagnets in future spintronic applications.…”

Voltage-controlled magnetic solitons motion in an anisotropic ferromagnetic nanowire

“…Magnetic materials play a vital role in modern information storage, compared to traditional semiconductor memory, they possess higher stability and reliability characteristics [1][2][3][4][5][6]. Magnetic solitons on the ferromagnetic nanoscale have been studied extensively as information carriers for memory storage device applications [7][8][9][10][11][12].…”

“…Meanwhile, high current densities are impractical for device applications [13][14][15]. The characteristic dispersion of the magnetic field generally increases the difficulty of manipulate [5,16]. Temperature gradient and spin wave-driven methods have been relatively neglected due to their experimental challenges [17][18][19][20].…”

The skyrmion bags in an anisotropy gradient

“…Besides that, another method that has been proved to be efficient in controlling the spin textures is based on the voltage-controlled magnetic anisotropy (VCMA) effect [24,25]. Based on this strategy, the magnetic anisotropy gradient has been widely used in the manipulation of spin textures [26][27][28][29][30][31][32][33][34][35]. Skyrmion bags, as spin textures with arbitrary topological charge [36][37][38], are expected to become the information carriers for multiple-data and high-density racetrack memory [39][40][41] and interconnect device [42,43].…”