Magnetic ordering in Ho‐doped Bi2Te3 topological insulator

We investigate the magnetic properties of Ho‐doped Bi₂Te₃ thin films grown by molecular beam epitaxy. Analysis of the polarized X‐ray absorption spectra at the Ho M₅ absorption edge gives an effective 4f magnetic moment which is ～45% of the Hund's rule ground state value. X‐ray magnetic circular dichroism (XMCD) shows no significant anisotropy, which suggests that the reduced spin moment is not due to the crystal field effects, but rather the presence of non‐magnetic or antiferromagnetic Ho sites. Extrapolating the temperature dependence of the XMCD measured in total electron yield and fluorescence yield mode in a field of 7 T gives a Curie–Weiss temperature of ?_CW ≈ –30 K, which suggests antiferromagnetic ordering, in contrast to the paramagnetic behavior observed with SQUID magnetometry. From the anomaly of the XMCD signal at low temperatures, a Néel temperature T_N between 10 K and 25 K is estimated. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)