In-plane antiferromagnetic moments and magnetic polaron in the axion topological insulator candidate EuIn2As2

Topological insulator with antiferromagnetic order can serve as an ideal platform to realize axion electro-dynamics. In this paper, we report a systematic study of the axion topological insulator candidate EuIn2As2. A linear energy dispersion across the Fermi level reveals a hole-type Fermi pocket. The orientation of the magnetic moment for ground state is determined within the ab-plane by anisotropic magnetic behavior. Besides long-range antiferromagnetic order, magnetization and magnetotransport measurements indicate existence of the ferromagnetic orders and ferromagnetic correlation, suggesting the formation of the magnetic polarons. These ferromagnetic clusters can persist above the antiferromagnetic transition leading to unconventional transport properties. Our results suggest multiple magnetic orders and states in EuIn2As2, which is vital to understanding its topological nature.