Hrem and measurement of magnetic properties of Fe-clusters embedded in MgO films

Nanometer-sized bcc (α) and fcc (γ) Fe crystallites and clusters epitaxially embedded in single crystalline MgO films (Fe-MgO composite films) were prepared by an ultra-high vacuum co-deposition of Fe and MgO on NaCl (001) substrates. The atomic structure was analyzed in detail by high-resolution electron microscopy. The magnetic properties (M-T and M-H curves) were measured with a high-sensitivity SQUID apparatus or a Faraday-type magnetometer on the same samples. The samples showed a kind of super-paramagnetism with an enhancement of magnetization owing to an interface effect with MgO. The effect of nanometer-sized Fe crystallites and clusters of a few atoms on the magnetic properties is discussed on the basis of the experimental results.