Uditha M. Jayathilake

arXiv2026

Dual-Sublattice Ferromagnetism Driven by Cooperative Double Exchange and Superexchange at NdNiO$_3$/CaMnO$_3$ Interfaces

Engineering emergent ferromagnetism at correlated-oxide interfaces offers a powerful route to creating collective states that do not exist in the parent materials. Here, we show that interfacial valence reconstruction in NdNiO$_3$/CaMnO$_3$ superlattices generates dual-sublattice ferromagnetism involving both Mn and Ni. Depth-resolved standing-wave X-ray photoelectron spectroscopy reveals enhanced Mn$^{3+}$ character on the CaMnO$_3$ side of the interface and enhanced Ni$^{2+}$ character on the NdNiO$_3$ side, establishing the configurations required for Mn$^{4+}$-O-Mn$^{3+}$ double exchange and Ni$^{2+}$-O-Mn$^{4+}$ superexchange, respectively. At low temperature, element-specific XMCD reveals ferromagnetic responses from both sublattices, with the Ni response concentrated predominantly in the Ni$^{2+}$-derived spectral component that SW-XPS independently shows to be enhanced at the interface. Together, these results show that cooperative double exchange within CaMnO$_3$ and superexchange across the interface couple the Mn and Ni sublattices, providing a general strategy for engineering interfacial ferromagnetism in correlated oxides.

cond-mat.mtrl-sci↗

arXiv2026

Evolution of electronic and magnetic properties in Mn- and Co-alloyed ferromagnetic kagome metal Fe3Sn2

Kagome metals are an intriguing class of quantum materials as the presence of both flat bands and Dirac points provides access to functional properties present in strongly correlated and topological materials. To fully harness these electronic features, the ability to tune the Fermi level relative to the band positions is needed. Here we explore the structural, electronic and magnetic impacts of substitutional alloying within ferromagnetic kagome metal Fe3Sn2 in thin films grown by molecular beam epitaxy. Transition metals Mn and Co are chosen as substitutes for Fe to reduce or increase the d-band electron count, thereby moving the Fermi level accordingly. We find that Co is not incorporated into the Fe3Sn2 structure but instead results in a two-phase Fe-Co and (Fe,Co)Sn composite. In contrast, Fe3-xMnxSn2 films are realized with x up to 1.0, retaining crystalline quality comparable to the parent phase. The incorporation of Mn repositions the flat bands relative to the Fermi level in a manner consistent with hole-doping, as revealed by hard x-ray photoemission and density functional theory. The Fe3-xMnxSn2 films retain room temperature ferromagnetism, with x-ray magnetic circular dichroism measurements confirming that the Fe and Mn moments are ferromagnetically aligned. The ability to hole-dope this magnetic kagome metal provides a platform for tuning properties such as anomalous Hall and Nernst responses.

cond-mat.mtrl-sci↗