Unconventional magnetic interactions in thin films of the kagome magnet TbMn₆Sn₆

Kagome materials are being explored as platforms for realizing novel density waves, unconventional superconductivity, and topological magnetic metals. Despite intriguing findings in bulk crystalline samples, thin films are less studied. Here, we have studied the magnetic interactions between kagome layers in thin films of the magnetic metal TbMn₆Sn₆, grown directly on insulating LSAT(111) substrates using molecular beam epitaxy. In contrast to TbMn₆Sn₆ bulk samples, the out-of-plan magnetization curves of our thin films show evidence for coexistence of low and high-coercivity moments at low temperatures, the latter of which have similar coercivity as that observed in the anomalous Hall effect in transport measurements. X-ray magnetic circular dichroism experiment reveals that the Tb and Mn moments are ferrimagnetically aligned at high temperatures, with Tb moments aligned anti-parallel to the magnetic field. However, at low temperatures, we see evidence for Tb moments pointing parallel to the applied field, with paramagnetic-like properties. We also see evidence for a large paramagnetic moment in our films after accounting for the substrate magnetization. We interpret these results in terms of competing antiferromagnetic and ferromagnetic orders between the Mn Kagome layers in TbMn₆Sn₆ thin films at low temperatures.