Magnetic coupling at the interface between ultrathin tetragonal CuO and La 0 . 7 Sr 0 . 3 MnO 3

High -symmetry rocksalt type tetragonal CuO (T-CuO) does not exist in bulk but can be synthesized via thin film epitaxy limited to a few unit cells (3, 4) thick and above which it relaxes to its bulk tenorite structure. Direct probe into magnetic properties of T-CuO layer has been a challenge because of its ultrathin limit. Here, we demonstrate the interfacial magnetic coupling between ultrathin T-CuO and ferromagnetic (La 0 . 7 Sr 0 . 3 MnO 3 ) layers in an epitaxial CuO/La 0 . 7 Sr 0 . 3 MnO 3 bilayer grown on (001) -oriented SrTiO 3 . We observe a positive exchange bias shift of - 30 Oe at 2 K in CuO/La 0 . 7 Sr 0 . 3 MnO 3 bilayer. The observation of positive exchange bias indicates that there exists antiferromagnetic exchange coupling between Mn and Cu moments at the interface. Notably, the exchange bias vanishes at 5 K and it is discussed in view of the proposed spin structure revealed from low -energy muon spin rotation and x-ray magnetic circular dichroism study [Phys. Rev. B 103 , 224429 (2021)]. Furthermore, an enhanced Gilbert damping, linewidth broadening and larger inhomogeneous 4 pi M eff value from in -plane ferromagnetic resonance measurements, are the direct consequence of antiferromagnetic exchange coupling at the CuO/La 0 . 7 Sr 0 . 3 MnO 3 interface. Combining both static and dynamic magnetic characterization, we establish an understanding of interfacial exchange coupling in CuO/La 0 . 7 Sr 0 . 3 MnO 3 bilayer.