Magnetic properties of an iron ore sample after microwave heating

The effect of microwave radiation on the magnetic properties of an iron ore was investigated. Four samples from Choghart Iron ore were used in this research. Three samples were treated for 30, 60 and 120s respectively, in a multi mode microwave oven with a frequency of 2.45 GHz and a maximum power of 1100W. The magnetizations of non-treated and microwave-treated samples were determined using a vibrating sample magnetometer (VSM). With increasing in radiation time to 60s. the total magnetism saturation and remanent magnetization of the samples were increased. The results show that with further increasing in microwave radiation time up to 120s, localized sample melting was occurred and the total magnetism saturation and remanent magnetization were decreased. The results showed that the sample composes ferromagnetic and paramagnetic fractions. With increasing in microwave radiation time the magnetic susceptibility of the paramagnetic fraction was decreased from 0.0111 to zero whereas the magnetic susceptibility of the ferromagnetic fraction initially was increased from 0.0687 to 0.3879 then decreased to 0.1894 (at 120s radiation time). It was confirmed that microwave radiation has a significant effect upon magnetic properties of iron ore. However, there is a limited condition, excessive radiation has a negative effect and reduces the magnetic susceptibility of iron ore. (C) 2010 Elsevier B.V. All rights reserved.