Magnetic inhomogeneity in the copper pseudochalcogenide CuNCN

TL;DR

This study reveals that CuNCN exhibits an inhomogeneous magnetic ground state with coexisting frozen and dynamic components, emerging below 80 K and persisting down to 20 K, indicating complex magnetic behavior in this frustrated system.

Contribution

The paper provides the first comprehensive local-probe investigation demonstrating microscopic coexistence of frozen and dynamic magnetic states in CuNCN.

Findings

Magnetic inhomogeneity appears below 80 K.

Frozen and dynamic magnetic components coexist microscopically.

Dynamic component disappears below 20 K.

Abstract

Copper carbodiimide, CuNCN, is a geometrically frustrated nitrogen-based analogue of cupric oxide, whose magnetism remains ambiguous. Here, we employ a combination of local-probe techniques, including $^{63,\, 65}$Cu nuclear quadrupole resonance, $^{13}$C nuclear magnetic resonance and muon spin rotation to show that the magnetic ground state of the Cu$^{2+}$ ($S=1/2$) spins is frozen and disordered. Moreover, these complementary experiments unequivocally establish an onset of intrinsically inhomogeneous magnetic state at $T_h=80$ K. Below $T_h$, the low-temperature frozen component coexist with the remnant high-temperature dynamical component down to $T_l = 20$ K, where the latter finally ceases to exist. Based on a scaling of internal magnetic fields of both components we conclude that the two components coexist on a microscopic level.