Observations of magnetic coupling in Fe-based nanocrystalline alloy by high-temperature giant magneto-impedance effect

The giant magneto-impedance (GMI) effect for Fe73.5Cu1Nb3Si13.5B9 nanocrystalline ribbons is investigated in the temperature range between room temperature and 873K. The thermal dependence of GMI effect reveals the enhancement of Curie temperature of the amorphous matrix, reflecting the exchange coupling between the α-FeSi grains as well as the compositional changes of the amorphous matrix itself. However, the dipolar interaction between grains is suggested to be responsible for the non-zero GMI effect after the magnetic phase transition of the amorphous matrix.