Comment on "Unconventional Magnetism in a Nitrogen-Containing Analog of Cupric Oxide"

TL;DR

This paper critically evaluates the proposed magnetic model for CuNCN, demonstrating it does not support the RVB state and suggesting the magnetic state may be homogeneous, challenging prior interpretations of inhomogeneous magnetism.

Contribution

It refutes the applicability of the anisotropic triangular lattice model to CuNCN and questions the existence of an inhomogeneous magnetic state as previously claimed.

Findings

The ATL model does not apply to CuNCN.

The ATL model does not support the RVB ground state.

CuNCN's magnetic state may be homogeneous.

Abstract

In a recent Letter [PRL, 107, 047208 (2011)], Zorko et al. report on an "unexpected inhomogeneous magnetism" related to "a peculiar fragility" of the resonating-valence-bond (RVB) electronic state in the spin-1/2 quantum magnet CuNCN. Here, we show that: i) the spin model of the anisotropic triangular lattice (ATL), as proposed by Zorko et al., does not apply to CuNCN; ii) this model does not support the proclaimed RVB ground state in the relevant parameter range; iii) the magnetic state of CuNCN is not necessarily inhomogeneous.