Hydrogenated <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>PdCoO</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> : A layered Meta

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., <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:msub> <a:mi>PdCoO</a:mi> <a:mn>2</a:mn> </a:msub> </a:mrow> </a:math> ) 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 ( <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mrow> <c:msub> <c:mi>T</c:mi> <c:mi>c</c:mi> </c:msub> <c:mo>&gt;</c:mo> <c:mn>420</c:mn> <c:mtext> </c:mtext> <c:mtext> </c:mtext> <c:mi mathvariant="normal">K</c:mi> </c:mrow> </c:math> ) in inherently nonmagnetic <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" display="inline"> <f:mrow> <f:msub> <f:mi>PdCoO</f:mi> <f:mn>2</f:mn> </f:msub> </f:mrow> </f:math> through controlled hydrogenation while preserving the delafossite structure. This process induces layer-selective electron doping into <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"> <h:mrow> <h:msub> <h:mi>CoO</h:mi> <h:mn>2</h:mn> </h:msub> </h:mrow> </h:math> 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 <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline"> <j:mrow> <j:msub> <j:mi>CoO</j:mi> <j:mn>2</j:mn> </j:msub> </j:mrow> </j:math> 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.