Tailoring of paramagnetic (structurally ordered) nanometric grains separated by ferromagnetic (structurally disordered) grain boundaries: Isolating grain-boundary magnetic effects

Partially reordering heavily milled intermetallic alloys results in structurally and chemically ordered nanometric grains separated by structurally and chemically disordered grain boundaries. In systems with disorder induced ferromagnetism this structural microstructure causes a peculiar magnetic microstructure: paramagnetic grains separated by magnetically ordered (ferromagnetic) grain boundaries. This unusual structural-magnetic microstructure allows for the easy separation of the magnetic contribution of the grain boundaries. This contribution is found to be about 15%, suggesting that the grain boundary is a few atomic layers thick, in agreement with high-resolution transmission electron microscopy observations.