Thermodynamic and magnetic properties of the layered triangular magnet NaNiO2

TL;DR

This study investigates the magnetic and thermodynamic properties of NaNiO2, revealing long-range magnetic order below 19.5K, short-range correlations above this temperature, and complex magnetic cluster behavior extending above 25K.

Contribution

It provides comprehensive experimental insights into the magnetic phases and cluster dynamics of NaNiO2, a layered triangular antiferromagnet, including a partial magnetic phase diagram.

Findings

Long-range magnetic order below 19.5K.

Presence of short-range magnetic correlations above T_N.

Magnetic clusters persist above 25K and slow down at 3K.

Abstract

We report muon-spin rotation, heat capacity, magnetization, and ac magnetic susceptibility measurements of the layered spin-1/2 antiferromagnet NaNiO2. These show the onset of long-range magnetic order below T_N = 19.5K. Rapid muon depolarization persisting to about 5K above T_N is consistent with the presence of short-range magnetic order. The temperature and frequency dependence of the ac susceptibility suggests that magnetic clusters persist above 25K in the paramagnetic state and that their volume fraction decreases with increasing temperature. A frequency dependent peak in the ac magnetic susceptibility at T_sf = 3K is observed, consistent with a slowing of spin fluctuations at this temperature. A partial magnetic phase diagram is deduced.