Frustrated Heisenberg $J_1-J_2$ model within the stretched diamond lattice of LiYbO2

TL;DR

This study explores the complex magnetic behavior of LiYbO$_2$, revealing a spiral magnetic ground state driven by frustrated interactions on a stretched diamond lattice, with evidence of interactions beyond the classical Heisenberg model.

Contribution

It demonstrates how a Heisenberg $J_1-J_2$ model explains the spiral order but highlights limitations, indicating additional interactions influence the magnetic states.

Findings

LiYbO$_2$ exhibits a long-range incommensurate helical magnetic order.

Application of a magnetic field induces a lock-in to a commensurate phase.

The $J_1-J_2$ model explains the spiral wave vector but not all magnetic features.

Abstract

We investigate the magnetic properties of LiYbO$_2$, containing a three-dimensionally frustrated, diamond-like lattice via neutron scattering, magnetization, and heat capacity measurements. The stretched diamond network of Yb$^{3+}$ ions in LiYbO$_2$ enters a long-range incommensurate, helical state with an ordering wave vector ${\bf{k}} = (0.384, \pm 0.384, 0)$ that "locks-in" to a commensurate ${\bf{k}} = (1/3, \pm 1/3, 0)$ phase under the application of a magnetic field. The spiral magnetic ground state of LiYbO$_2$ can be understood in the framework of a Heisenberg $J_1-J_2$ Hamiltonian on a stretched diamond lattice, where the propagation vector of the spiral is uniquely determined by the ratio of $J_2/|J_1|$. The pure Heisenberg model, however, fails to account for the relative phasing between the Yb moments on the two sites of the bipartite lattice, and this detail as well as the presence of an intermediate, partially disordered, magnetic state below 1 K suggests interactions beyond the classical Heisenberg description of this material.