Giuseppe Buccoliero | Searcharxiv

arXiv2026

Ligand Mediated Magnetic Coupling Across Metamagnetic Transitions in CrPS4

Chromium thiophosphate (CrPS4) is a long-known material: a layered semiconducting antiferromagnet. Its recently discovered gate-tunable metamagnetic phase transitions, the remarkable positive and oscillating magnetoresistance as a tunnel barrier, and its Fano-resonance luminescence, elusive among the multitude of Cr3+ compounds, call for revisiting the understanding of its electronic structure, especially regarding how it relates to magnetic order. Here, we employ X-ray magnetic circular dichroism, implemented in both absorption and resonant inelastic X-ray spectroscopies, together with quantum many-body calculations, to unveil the role of metal-ligand covalency in mediating the metamagnetic transitions in CrPS4, using crystal-field and charge-transfer excitations as fingerprints of the evolving magnetic order. We reveal the role of extended superexchange paths involving P and S atoms, coupling interactions between the Cr spins across the different magnetic phases: antiferromagnetic, canted, and ferromagnetic. Our results elucidate the electronic states involved in these phases and provide prescriptions for engineering the metamagnetic phase diagram of CrPS4.

cond-mat.mtrl-sci↗

arXiv2025

In situ growth and magnetic characterization of Cr Chloride monolayers

Monolayer Chromium Dihalides and Trihalides materials can be grown on a variety of substrates by molecular beam epitaxy regardless of the lattice mismatch thanks to the van der Waals epitaxy. In this work, we studied the magnetic nature of Cr Chloride monolayers grown on Au(111), Ni(111) and graphene-passivated Ni(111) from the evaporation in ultra-high vacuum of the same halide precursor. Structural, morphological and magnetic characterizations were conducted in situ by low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and X-ray magnetic circular dichroism (XMCD). Owing to opposite chemical behaviour, Au(111) and Ni(111) promote the formation of two different valence compounds, i.e. CrCl$_3$ and CrCl$_2$, showing distinct magnetic properties at 4 K. When graphene is used to passivate the Ni(111) surface, the formation of CrCl$_3$ becomes allowed also on this substrate. The coexistence of CrCl$_3$ and CrCl$_2$, both showing few nm lateral size and super-paramagnetic properties, is demonstrated by XMCD spectra displaying two dichroic peaks at the characteristic Cr$^{3+}$ and Cr$^{2+}$ energies. Site-selective magnetization measurements performed with the photon energy tuned on the two absorption edges show reversed magnetization of some of the CrCl$_2$ islands with respect to the CrCl3 domains, which is interpreted in terms of magnetic frustration.

cond-mat.mtrl-sci↗