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Hydrogenated PdCoO2: A layered Metallic Oxide with Robust Room-Temperature Ferromagnetism

Di Tian1,*, Haotian Zheng2,*, Zewei Huang1,*, Sijie Wu1, Pengcheng Li3, Cong Li1, Jianbing Zhang1, Xinyu Shu1,4, Jinling Zhou1 et al.

Yang Liu1, Yanhong Gu1, Meng Wang5, Di Yi3,6, Tianxiang Nan7, Zhen Chen8,9, Qing He10, Huaqiang Wu7, Shuyun Zhou1,11, Weidong Luo2,†, and Pu Yu1,11,‡

  • *These authors contributed equally to this work.
  • †Contact author: wdluo@sjtu.edu.cn
  • ‡Contact author: yupu@mail.tsinghua.edu.cn
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Phys. Rev. X 15, 041030 – Published 14 November, 2025

DOI: https://doi.org/10.1103/3mgc-z9wv

Abstract

Layered oxide materials, with their two-dimensional crystalline architectures and tunable interlayer interaction, serve as a fertile field for harnessing emergent quantum phenomena. Among these materials, metallic delafossites (e.g., PdCoO2) have emerged as a prominent system with extraordinary two-dimensional electronic properties, though their intrinsic lack of ferromagnetism has remained a fundamental constraint. Here, we report the creation of robust, bulk high-temperature ferromagnetism (Tc>420  K) in inherently nonmagnetic PdCoO2 through controlled hydrogenation while preserving the delafossite structure. This process induces layer-selective electron doping into CoO2 layers, stabilizing Ising-type ferromagnetism with pronounced perpendicular magnetic anisotropy while preserving the material’s exceptional metallicity. Remarkably, the system self-assembles into a superlattice of alternating metallic Pd and insulating ferromagnetic hydrogenated CoO2 layers, enabling an unconventional anomalous Hall effect mediated by interlayer spin-charge coupling. These findings demonstrate that bulk ferromagnetism can be achieved in delafossite oxides while preserving their structural integrity, positioning hydrogenated delafossites as a versatile platform for exploring correlated quantum effects and designing multifunctional devices.

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Layered oxide materials, made of stacked 2D sheets, offer a powerful platform for exploring exotic quantum behaviors such as superconductivity and ferroelectricity. Among these, metallic delafossites are especially intriguing because they combine remarkable electronic properties with naturally layered crystal structures. A prime example is PdCoO2, which exhibits electrical conductivity rivaling that of noble metals such as gold, silver, and platinum. However, its application potential has been limited by a lack of magnetism—its cobalt ions normally exist in a nonmagnetic state. We show that a delafossite can show ferromagnetism at room temperature.

We successfully introduce strong ferromagnetism in PdCoO2 by carefully heating the material at moderate temperature in a hydrogen-rich environment. This treatment intercalates hydrogen atoms into the lattice that trigger a chemical transformation within the cobalt oxide layers, converting nonmagnetic cobalt ions into magnetic ones through a spin-state transition. As a result, the system develops a robust magnetic order that persists well above room temperature. Despite this change, the material retains its excellent electrical conductivity because the conductive palladium layers remain largely unaffected. The process also causes the layers to reorganize into a natural superlattice of alternating metallic and magnetic sheets, giving rise to some exotic electronic effects.

By activating hidden magnetic behavior in PdCoO2, we demonstrate a way to engineer magnetism in materials that were previously considered nonmagnetic. This paves the way for designing delafossites with a unique electronic dichotomy with coupled spin and charge degrees of freedom, expanding opportunities for next-generation spintronic devices.

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Phys. Rev. X 15, 041030– Published 14 November, 2025
  • Received 25 June 2025
  • Accepted 16 October 2025
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