Competing spin modulations in a magnetically frustrated semimetal EuCuSb

TL;DR

This study investigates the complex magnetic ground states of EuCuSb, revealing competing spin modulations and their impact on electronic properties through comprehensive experimental techniques.

Contribution

It uncovers the coexistence of collinear and helical spin modulations in EuCuSb and links these to its frustrated magnetic interactions and electronic behavior.

Findings

EuCuSb exhibits collinear up-up-down-down spin order below 8.5 K.

Partial helical spin modulation appears below 6 K.

Anomalous magnetoresistance indicates competing magnetic ground states.

Abstract

The competing magnetic ground states of the itinerant magnet EuCuSb, which has a hexagonal layered structure, were studied via magnetization, resistivity, and neutron diffraction measurements on single-crystal samples. EuCuSb has a three-dimensional semimetallic band structure as confirmed by band calculation and angle-resolved photoelectron spectroscopy, consistent with the nearly isotropic metallic conductivity in the paramagnetic state. However, below the antiferromagnetic transition temperature of TN1 (8.5 K), the resistivity, especially along the hexagonal axis, increases significantly. This implies the emergence of anisotropic magnetic ordering coupled to the conducting electrons. Neutron diffraction measurements show that the Eu spins, which order ferromagnetically within each layer, are collinearly modulated (up-up-down-down) along the hexagonal axis below TN1, followed by the partial emergence of helical spin modulation below TN2 (6 K). Based on the observation of anomalous magnetoresistance with hysteretic behavior, we discuss the competing nature of the ground state inherent in a frustrated Heisenberg-like spin system with a centrosymmetric structure.