SPICE Workshop on Hybrid Correlated States and Dynamics in Quantum Materials, May 14th - 16th 2024
Olena Gomonay
We present a phenomenological theory of altermagnets, able to describe their unique magnetization dynamics and to model magnetic textures in this emergent collinear magnetic ordered phase, having zero-net magnetization and
alternating spin-polarization in the non-relativistic electronic band structure. Focusing on the prototypical d-wave altermagnets, e.g. RO$_2$,
we can explain intuitively the unique lifted degeneracy of their magnon spectra, by
the emergence of an effective sublattice-dependent anisotropic spin stiffness arising naturally from the phenomenological theory.
We show that the altermagnetic domain walls, in contrast to antiferromagnets, have a finite gradient of the magnetization projection along the easy axis orientation, with its strength and direction connected to the altermagnetic anisotropy, even for 180$^\circ$ domain walls. This gradient generates a ponderomotive force in the domain wall in the presence of an external magnetic field.
The motion of these altermagentic domain walls are also characterized by an anisotropic Walker breakdown, with much higher speed limits of propagation than ferromagnets but lower than antiferromagnets. Finally, also in contrast to antiferromagnetic and ferromagnetic domain walls, we demonstrate magnon scattering from unpinned domain walls, which can lead to domain wall manipulation by magnonic currents,
polarized along the easy axis orientation for the case of RuO$_2$.