Bakr Mohamed

Structural, microstructural, magnetic and electrical properties of diluted magnetic Se1−xMnx

Polycrystalline Se1?xMnx (x?=?0.01, 0. 03 and 0.05) samples were prepared by solid state reaction. The x-ray analysis using Rietveld method revealed the presence of two phases in the Se1?xMnx matrix; the Se phase and MnSe phase. The magnetization measurement showed three peaks at; 270, 160 and 150?K. The two peaks at 150?K and 160?K are due to antiferromagnetic transition, but the peak at 270?K is due to magnetic structural phase transition. The ac conductivity was measured under vacuum in the temperature range 77?493?K and frequency range 50?Hz?100?kHz. The ac conductivity results showed that samples Se0.99Mn0.01 and Se0.97Mn0.03 follow the overlapping large polaron tunnelling model, while sample Se0.95Mn0.05 follows the correlated barrier hopping model. The barrier height Wm is getting smaller by increasing the localization defects centres, caused by increasing the Mn per cent. Accordingly the Se0.95Mn0.o5 sample has the smallest Wm and consequently the largest ac conductivity, dielectric constant (?1) and dielectric loss (?2). The dielectric constant is three orders higher than those of pure Se element. The temperature dependence of ?1 and ?2 revealed anomaly peaks at nearly room temperature, caused by the structural phase transition. The antiferromagnetic and the high dielectric properties of the studied samples make them a good material for electromagnetic devices that can be used in many applications.