Nanocrystalline two-phase composite magnets consisting of a fine mixture of grains of the soft phase uniformly distributed in the magnetically hard and soft phases have attracted much attention for potential permanent magnet development [1]. The first one-dimensional model to explain the superior magnetic behavior of the nanocomposite magnet was reported by Kneller and Hawig [2, 3] who predicted that the highest coercivity can be achieved by the exchange coupling force when the size of soft magnetic phase is twice as big as the domain wall width of the hard magnetic phase (~ 20 nm). Magnetic characters of the nanocomposite magnets are influenced sensitively by their microstructures such as the volume ratio between hard and soft magnetic phases, the grain sizes and their uniform distribution [4]. In addition, it was found that the alloy