Magnetic order of tetragonal CuO ultra-thin films

Abstract

We present a detailed low-energy muon spin rotation and x-ray magnetic circular dichroism (XMCD) investigation of the magnetic structure in ultra-thin tetragonal (T)-CuO films. The measured muon-spin polarization decay indicates an antiferromagnetic (AFM) order with a transition temperature higher than 200K. The XMCD signal obtained around the Cu $L_{2,3}$ edges indicates the presence of pinned Cu${}^{2+}$ moments that are parallel to the sample surface, and additionally, isotropic paramagnetic moments. The pinning of some of the Cu moments is caused by an AFM ordering consisting of moments that lie most likely in the plane of the film. Moreover, pinned moments show a larger orbital magnetic moment contribution with an approximate ratio of $m_{orb}/m_{spin}=2$, indicating that these spins are located at sites with reduced symmetry. Some fractions of the pinned moments remain pinned from an AFM background even at 360K, indicating that $T_N>$ 360K. A simple model could explain qualitatively these experimental findings; however, it is in contrast to theoretical predictions, showing that the magnetic properties of ultra-thin T-CuO films differ from bulk expectations and is more complex.

arXiv comment11 Figures

References in corpus (8)

• Intense paramagnon excitations in a large family of high-temperature superconductors
• Multiplet ligand-field theory using Wannier orbitals
• Origin of interface magnetism in BiMnO3/SrTiO3 and LaAlO3/SrTiO3 heterostructures
• Tetragonal CuO: A new end member of the 3d transition metal monoxides
• Magnetic and electronic properties at the gamma-Al2O3/SrTiO3 interface
• Do topology and ferromagnetism cooperate at the EuS/Bi${}_2$Se${}_3$ interface?
• Direct spectroscopic observation of a shallow hydrogen-like donor state in insulating SrTiO${}_3$
• Generalized one-band model based on Zhang-Rice singlets for Tetragonal CuO