We investigated static and dynamic magnetic properties of surfactant capped 25 nm Co50Ni50 particles. These nanoparticles exhibit the superparamagnetic behavior at 300 K. Interestingly, a freezing temperature (T-f similar to 16 K) is observed in the ZFC curve, which corresponds to surface spin-glass-like transition. The significant high coericivity (H-c similar to 910 Oe) is observed at 5 K as compared to H-c similar to 180 Oe at 77 K and is attributed to the random freezing of surface spins at T <= T-f. The spin-glass-like behavior of nanoparticles is further verified by ac-susceptibility measurements as a function of temperature at different frequencies. The fits of Arrhenius law, Vogel-Fulcher law and dynamic scaling equation to data confirm the spin-glass-like behavior of Co50Ni50 nanoparticles. (C) 2013 Elsevier B.V. All rights reserved.