Magnetic model for A2CuP2O7 (A = Na, Li) revisited: 1D versus 2D behavior

TL;DR

This study revises the magnetic model of A2CuP2O7 compounds, demonstrating they are quasi-one-dimensional magnets with specific exchange interactions, confirmed by high-field magnetization measurements and quantum simulations.

Contribution

It provides a definitive quasi-one-dimensional magnetic model for A2CuP2O7, contrasting previous two-dimensional assumptions, supported by experimental and computational evidence.

Findings

Magnetization data confirms 1D magnetic behavior.

Exchange interactions are consistent with a 27 K intrachain coupling.

Long-range order is discussed in context of experimental data.

Abstract

We report magnetization measurements, full-potential band structure calculations, and microscopic modeling for the spin-1/2 Heisenberg magnets A2CuP2O7 (A = Na, Li). Based on a quantitative evaluation of the leading exchange integrals and the subsequent quantum Monte-Carlo simulations, we propose a quasi-one-dimensional magnetic model for both compounds, in contrast to earlier studies that conjectured on the two-dimensional scenario. The one-dimensional nature of A2CuP2O7 is unambiguously verified by magnetization isotherms measured in fields up to 50 T. The saturation fields of about 40 T for both Li and Na compounds are in excellent agreement with the intrachain exchange J1 ~ 27 K extracted from the magnetic susceptibility data. The proposed magnetic structure entails spin chains with the dominating antiferromagnetic nearest-neighbor interaction J1 and two inequivalent, nonfrustrated antiferromagnetic interchain couplings of about 0.01*J1 each. A possible long-range magnetic ordering is discussed in comparison with the available experimental information.