The free energy of twisting spins in Mn${}_3$Sn

Abstract

The magnetic free energy is usually quadratic in magnetic field and depends on the mutual orientation of the magnetic field and the crystalline axes. Tiny in magnitude, this magnetocrystalline anisotropy energy (MAE) is nevertheless indispensable for the existence of permanent magnets. Here, we show that in Mn${}_3$Sn, a non-collinear antiferromagnet attracting much attention following the discovery of its large anomalous Hall effect, the free energy of spins has superquadratic components, which drive the MAE. We experimentally demonstrate that the thermodynamic free energy includes terms odd in magnetic field ($\mathcal{O}(H^3)+\mathcal{O}(H^5)$) and generating sixfold and twelve-fold angular oscillations in the torque response. We show that they are quantitatively explained by theory, which can be used to quantify relevant energy scales (Heisenberg, Dzyaloshinskii-Moriya, Zeeman and single-ion anisotropy) of the system. Based on the theory, we conclude that, in contrast with common magnets, what drives the MAE in Mn${}_3$Sn is the field-induced deformation of the spin texture.

6 pages, 5 figures, Supplemental Material is included

References in corpus (12)

• Electrical Manipulation of a Topological Antiferromagnetic State
• Topological Weyl semimetals in the chiral antiferromagnetic materials Mn3Ge and Mn3Sn
• Cluster multipole theory for anomalous Hall effect in antiferromagnets
• Anomalous and topological Hall effects in epitaxial thin films of the noncollinear antiferromagnet Mn${}_3$Sn
• Chiral domain walls of Mn${}_3$Sn and their memory
• Comparing the anomalous Hall effect and the magneto-optical Kerr effect through antiferromagnetic phase transitions in Mn${}_3$Sn
• Antichiral spin order its Goldstone modes and their hybridization with phonons in the topological semimetal Mn3Ge
• Giant effective damping of octupole oscillation in an antiferromagnetic Weyl semimetal
• A mono-material Nernst thermopile with hermaphroditic legs
• Observation of spontaneous x-ray magnetic circular dichroism in a chiral antiferromagnet
• Anisotropic magnetic interactions in hexagonal AB-stacked kagome lattice structures: Applications to ${\mathrm{Mn}}_3\mathrm{X}$ ($\mathrm{X}$ = $\mathrm{Ge}$, $\mathrm{Sn}$, $\mathrm{Ga}$) compounds
• Anomalous thermal Hall effect in the topological antiferromagnetic state

Cited by in corpus (4)

• Magnetostriction, piezomagnetism and domain nucleation in a kagome antiferromagnet
• Order parameter dynamics in Mn${}_3$Sn driven by DC and pulsed spin-orbit torques
• Impact of strain on the SOT-driven dynamics of thin film Mn${}_3$Sn
• Magnetic Moiré Systems: a review