Magnetic Phase Transitions in Zn1−x Mn x O
Abstract
Thermal diffusivity measurements have been used to study the magnetic phase transitions in ZnO doped with Mn. The temperature dependencies of the thermal diffusivity in the wide temperature range from 70 to 300 K reveal an inverted-lambda-shaped peak at a temperature of 75 K for Zn0.95Mn0.05O doped with nitrogen and additional peaks at 117 K and 122 K for the nitrogen-doped and the undoped Zn0.95Mn0.05O samples, respectively. The lambda-shaped peak demonstrates the existence of a second order phase transition in these samples. The thermal diffusivity peak at 75 K was attributed to a ferromagnetic-paramagnetic phase transition in the Zn0.95Mn0.05O doped with nitrogen, and the peaks at 117 K and 122 K were attributed to an antiferromagnetic-paramagnetic phase transition in the MnO nanoclusters.