Magnetic inhomogeneity in the copper pseudochalcogenide CuNCN

Abstract

Copper carbodiimide, CuNCN, is a geometrically frustrated nitrogen-based analog of cupric oxide, whose magnetism remains ambiguous. Here, we employ a combination of local-probe techniques, including Cu63,65 nuclear quadrupole resonance, C13 nuclear magnetic resonance, and muon spin rotation to show that the magnetic ground state of the Cu2+ (S=1/2) spins is frozen and disordered. Moreover, these complementary experiments unequivocally establish the onset of an intrinsically inhomogeneous magnetic state at Th=80 K. Below Th, the low-temperature frozen component coexists with the remnant high-temperature dynamical component down to Tl=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.