Although alpha ''-Fe16N2-like compounds exhibit enhanced magnetization compared to alpha-Fe, it is important to increase their magnetic coercivity to obtain new hard magnetic materials for electric vehicle application. In the present work, coarse FePt particles were coated with finely powdered Fe3O4 produced by the hydrolysis of Fe (acac)(3) in benzyl alcohol. This Fe3O4 coating layer was subsequently reduced under hydrogen and then nitrided by ammonolysis at 150 degrees C to obtain a dual-phase mixture of an alpha ''-Fe16N2-like compound (referred to herein as "alpha ''-Fe16N2") and residual alpha-Fe. The ("alpha ''-Fe16N2" + alpha-Fe)(1-x)/(FePt)(x) composite particles for which x = 0.2, 0.4 or 0.6 generated smooth magnetization hysteresis curves, and the magnetic coercivity of these materials increased with increases in the proportion of FePt. Magnetic coupling was clearly evident between the core and shell regions in the composite powder for which x = 0.6, as demonstrated by a plot of the Wohlfarth interaction against the magnetic field. Transmission electron microscopy images confirmed magnetic coupling between the coarse FePt particles (several hundred nm in diameter) and the coating of fine mixed particles (several tens of nm in diameter) of "alpha ''-Fe16N2" and alpha-Fe. The "alpha ''-Fe16N2" crystals forming the particle shell were found to grow epitaxially, aligning their c-axes parallel to that of the tetragonal FePt.