RuO2 has been proposed as the prototypical altermagnetic material. However, several reports have recently questioned its intrinsic magnetic ordering, leading to conflicting findings, especially in thin film heterostructures pointing to possible interface effects being convoluted with supposed antiferromagnetic/altermagnetic signatures. Here, extensive magnetometry measurements were performed on two independently grown thin film heterostructures of RuO2 interfaced with either NiFe or Fe acting as the ferromagnetic layer. Below about 15 K, both samples exhibit exchange bias fields when cooled to approximately 2 K in a +1 T field, and a spin transitional feature is observed around 31 K. Magneto-Raman measurements on RuO2 thin films only reveal a magnon mode when there is a NiFe layer, suggesting that RuO2 does not intrinsically possess long range magnetic ordering.. When in contact with a ferromagnet, RuO2 displays effects that could be ascribed to antiferromagnetism. However, the lack of intrinsic magnon modes points toward possible diffusion between the layers or spin disorder at the interface as seen by density functional theory (DFT) calculations.
@article{arxiv.2508.15004,
title = {Probing Magnetic Properties of RuO$_{2}$ Heterostructures Through the Ferromagnetic Layer},
author = {Frank M. Abel and Subhash Bhatt and Shelby S. Fields and Vinay Sharma and Dai Q. Ho and Daniel Wines and D. Quang To and Joseph C. Prestigiacomo and Tehseen Adel and Riccardo Torsi and Maria F. Munoz and David T. Plouff and Xinhao Wang and Brian Donovan and Don Heiman and Gregory M. Stephen and Adam L. Friedman and Garnett W. Bryant and Anderson Janotti and Michelle E. Jamer and Angela R. Hight Walker and John Q. Xiao and Steven P. Bennett},
journal= {arXiv preprint arXiv:2508.15004},
year = {2025}
}