Weak itinerant magnetic phases of La2Ni7

TL;DR

This study investigates the magnetic phases of La2Ni7 using neutron diffraction, revealing incommensurate and commensurate magnetic orders and their temperature evolution, confirming theoretical predictions and detailing complex magnetic behavior.

Contribution

It provides detailed neutron diffraction data on La2Ni7's magnetic phases, identifying propagation vectors and moment directions across temperature ranges, advancing understanding of its itinerant magnetism.

Findings

Identified incommensurate and commensurate magnetic phases.

Mapped temperature-dependent magnetic propagation vectors.

Confirmed DFT predictions of low-temperature magnetic order.

Abstract

La2Ni7 is an intermetallic compound that is thought to have itinerant magnetism with a small moment ordering below 65 K. A recent study of single crystal samples by Ribeiro et. al. [Phys. Rev. B 105, 014412 (2022)] determined detailed anisotropic H-T phase diagrams and revealed three zero-field magnetic phase transitions at T1 ~ 61.0 K, T2 ~ 56.5K, and T3 ~ 42 K. In that study only the highest temperature phase is shown to have a clear ferromagnetic component. Here we present a single crystal neutron diffraction study determining the propagation vector and magnetic moment direction of the three magnetically ordered phases, two incommensurate and one commensurate, as a function of temperature. The higher temperature phases have similar, incommensurate propagation vectors, but with different ordered moment directions. At lower temperatures the magnetic order becomes commensurate with magnetic moments along the c direction as part of a first-order magnetic phase transition. We find that the low-temperature commensurate magnetic order is consistent with a proposal from earlier DFT calculations.