Optical and magneto-optical study of the magnetic phase diagram and incommensurate magnetic phase of NiBr2 and Ni1–xZnxBr2

Abstract

The variations of the 6000 Å band system with temperature from 4.2 to 30 K and magnetic fields up to 3 T applied parallel to the basal plane have been used to map the magnetic phase diagram of NiBr₂ and Ni_1–xZn_xBr₂(x= 0.05, 0.08). For NiBr₂ precise measurements are also reported of the temperature dependence of the wavelength of the two sharp exciton–magnon lines near 6080 Å, and of their behaviour in magnetic fields up to 16 T applied parallel to the c-axis and their polarisation.