Properties of axion insulator candidate layered Eu&lt;sub&gt;1–&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt;Ca&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt;In&lt;sub&gt;2&lt;/sub&gt;As&lt;sub&gt;2&lt;/sub&gt;

En-Kui Yi,Bin Wang,Bing Shen,Han Shen

doi:10.7498/aps.70.20210042

Abstract

The study of two-dimensional (2D) magnetic materials has driven the development of modern nano-electronic devices. Exploration of novel intrinsic layered materials with 2D magnetic order will provide a material candidate pool for fabricating 2D devices and searching for new quantum phases. Recently the layered antiferromagnetic (AF) topological insulators have aroused the great interest of researchers. As one of the proposed axion insulators, EuIn2As2 exhibits a layered structure and 2D AF order. It is found that the parent compound EuIn2As2 exhibits metallic behavior instead of the predicted insulating feature. To pursuit the predicted non-trivial topological state and novel feature, in this paper, we use various elements to dope the system to adjust the Fermi level. It is found that only Ca is successfully doped into the EuIn2As2 system. The systematic transport and magnetization studies are performed on the single crystal of Eu1–xCaxIn2As2. The long-range AF order is revealed to be similar to the parent compound. Above the AF transition, the magnetization violated Curie-Weiss behavior and magnetoresistance keeps negative, indicating the ferromagnetic order. With doping nearly 20% non-magnetic Ca, the magnetic properties of the system barely change, which is favorable to keeping the former predicted nontrivial topological properties in EuIn2As2. Although Ca shares the same valence with Eu, the carrier density of Eu1–xCaxIn2As2 is one order lower than that of EuIn2As2. The Ca doping brings electrons in and lifts the Fermi level. The results enrich the 2D magnetic material candidate pool and provide useful information for realizing the nontrivial topological state in the 2D AF system.

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