gamma-(Fe,Ni) alloy nanostructures were prepared by solution phase reduction in the system of surfactant-cyclohexane-water, which were characterized by means of transmission electron microscopy (TEM), selected-area electron diffraction pattern (SAED), powder X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). By modifying the micelles system, such as changing the kinds of surfactant and the concentrations of metal ions, the alloy nanostructures can be tunable in size and shape. Only spheres with diameter of ca. 70 nm and the mixture of spheres and sheets of the nanoalloys were obtained without and in the presence of cyclohexane, respectively. The sphere size can be tuned from 70 to 25 nm in diameter by changing the concentrations of metal ions. The lower concentrations of metal ions were useful for preparing tinier particles; the higher concentrations of metal ions promoted the forming of rods-like nanoparticles. The values of remnant magnetization Mr and covercivity He increased with the alloy diameters decreasing. (c) 2006 Elsevier B.V. All rights reserved.