Magnetic frustration in a van der Waals metal CeSiI

TL;DR

This paper reports the discovery of a van der Waals material, CeSiI, that exhibits coexistence of itinerant electrons and magnetic frustration, providing a new platform for exploring exotic magnetic phenomena in low-dimensional systems.

Contribution

It introduces CeSiI as a novel vdW material hosting both itinerant electrons and frustrated magnetism, confirmed through resistivity, magnetometry, and neutron diffraction measurements.

Findings

CeSiI exhibits dominant antiferromagnetic exchange below 7 K.

Neutron diffraction reveals incommensurate magnetic order with a specific propagation vector.

Magnetic field induces a two-step phase transition indicating magnetic frustration.

Abstract

The realization of magnetic frustration in a metallic van der Waals (vdW) coupled material has been sought as a promising platform to explore novel phenomena both in bulk matter and in exfoliated devices. However, a suitable material platform has been lacking so far. Here, we demonstrate that CeSiI hosts itinerant electrons coexisting with exotic magnetism. In CeSiI, the magnetic cerium atoms form a triangular bilayer structure sandwiched by van der Waals stacked iodine layers. From resistivity and magnetometry measurements, we confirm the coexistence of itinerant electrons with magnetism with dominant antiferromagnetic exchange between the strongly Ising-like Ce moments below 7 K. Neutron diffraction directly confirms magnetic order with an incommensurate propagation vector k ~ (0.28, 0, 0.19) at 1.6 K, which points to the importance of further neighbor magnetic interactions in this system. The presence of a two-step magnetic-field-induced phase transition along c axis further suggests magnetic frustration in the ground state. Our findings provide a novel material platform hosting a coexistence of itinerant electron and frustrated magnetism in a vdW system, where exotic phenomena arising from rich interplay between spin, charge and lattice in low dimension can be explored.