Magnetization distribution in Nd4.5Fe77B18.5 nanocomposite magnets studied by electron holography

Magnetic nanostructures at demagnetized and remanent states in Nd4.5Fe77B18.5 nanocomposite magnets are investigated by electron holography, utilizing the specially designed electromagnet. The quantitative mapping of magnetization distribution at a nanometer scale using a polar diagram has been reported for both the demagnetized and remanent states. Through the polar diagrams for the remanent state, the homogeneous distribution of magnetic flux is found in the specimen annealed at a low temperature, while the fluctuated distribution is found in the specimen annealed at a high temperature. The difference is considered to be responsible for their magnetic properties, i.e., remanence and coercivity. (C) 2004 American Institute of Physics.