Incommensurate magnetic orders and topological Hall effect in the square-net centrosymmetric EuGa2Al2 system

Neutron diffraction on the centrosymmetric square-net magnet EuGa2Al2 reveals multiple incommensurate magnetic states (AFM1, 2, 3) in zero field. In applied field, a new magnetic phase (A) is identified from magnetization and transport measurements, bounded by two of the mu H-0 = 0 incommensurate magnetic phases (AFM1, helical, and AFM3, cycloidal) with different moment orientations. Moreover, magnetotransport measurements indicate the presence of a topological Hall effect, with maximum values centered in the A phase. Together, these results render EuGa2Al2 a material with noncoplanar or topological spin texture in applied field. X-ray diffraction reveals an out-of-plane (OOP) charge density wave (CDW) below T-CDW similar to 50 K while the magnetic propagation vector lies in plane below T-N = 19.5 K. Together these data point to a new route to realizing in-plane noncollinear spin textures through an OOP CDW. In turn, these noncollinear spin textures may be unstable against the formation of topological spin textures in an applied field.

Automated summary

Neutron diffraction and X-ray diffraction techniques were used to study the magnetic and charge density wave properties of EuGa2Al2 material. Results showed the existence of multiple incommensurate magnetic states in zero field and the discovery of a new magnetic phase under applied field. Magnetotransport measurements also indicated the presence of a topological Hall effect, revealing the noncoplanar or topological spin texture characteristics of EuGa2Al2 under applied field.