A Phenomenological Approach for Understanding the High Magnetic Coercivity State of a Fe–O Nanocrystalline Press Compact

Experimentally obtained magnetic signals for a Fe-O nanocrystalline press-compact were fitted using a phenomenological approach. This method considers the individual properties of microvolumes and their statistics. It also helps avoiding complex calculations while focusing on local fundamental magnetic characteristics without considering internal processes. Currently, the precise estimation of internal processes in local areas is nearly impossible. They depend on fluctuations in the anisotropy field, texture degree, and phase ratio. A cubic compact (10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> volume) was fabricated by pressing magnetite particles mixed with 20% iron by weight in a high-energy milling machine. After characterizing the compacts by X-ray diffraction, their magnetic signals were measured to obtain the saturation magnetization (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> = 0.97 T) residual magnetization (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 0.456 T) and coercivity (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Н</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">с</sub> = 0.685 kOe). The results suggest that the particle anisotropy fields relate to the effective anisotropy constants from the interaction between iron and magnetite particles. It is also found that single domains formed by iron particles contribute to high coercive states. This confirms that increasing the degree of texture results in an increment of the relative remanence and coercivity.