Effect of Temperature on the Structural, Magnetic, and Microwave Electromagnetic Properties of Manganese Nitrides

Abstract

Mn doped with various loadings of nitrogen was prepared by nitridation of a micron α-Mn powder in a flowing ammonia atmosphere at a range of temperatures from 400 to 900 °C. X-ray diffraction (XRD) studies reveal that doping nitrogen content increases as the temperature rising from 400 to 600 °C and then decreases from 600 to 900 °C. A mass of ε-Mn₄N started to form during the heat treatment of α-Mn powder at 900 °C. The structural morphology and grain size of the products were carried out using scanning electron microscope (SEM). Vibration sample magnetometer (VSM) and vector network analyzer (VNA) were employed to investigate the effect of nitrogen doping on the magnetic and electromagnetic performance of the as-synthesized samples. Odd circles were found in the $\varepsilon ^{\prime } - \varepsilon ^{\prime \prime }$ figure, which may come from the interaction between electron charge and applied field. In addition, sphere Landau-Lifshitz-Gilbert (LLG) equation fitting approach is adopted to explain the magnetic resonance of the 900 °C sample. The composite of the 900 °C sample exhibits a wider frequency range for microwave absorption applications than other composites. The sample with a thickness of 7 mm shows two absorption peaks at about 3.6 and 14.48 GHz with the maximum reflection loss of −28.71 dB at 11.18 GHz and the absorption range below −5 dB from 2 to 18 GHz.