The magnetic properties of coated Au nanoparticles were investigated. Previous experimental results have shown that pure NiB and CoB amorphous particles are paramagnetic and ferromagnetic, respectively. The citrate-Au@NiB from Figure and the citrate-Au@CoB from Figure were used for magnetic studies. Citrate-Au@CoB nanoparticles exhibit ferromagnetic behavior that persists up to room temperature. Figure shows hysteresis in the field dependence of the magnetization with finite remanence up to 300K. The temperature dependence of the magnetization shown in Figure suggests a magnetic transition temperature above room temperature. Citrate-Au@NiB nanoparticles show transitions from ferromagnetic to superparamagnetic to paramagnetic across the temperature range 5-300K. At low temperatures, the Ni nanoparticles exhibit ferromagnetic behavior with hysteretic field dependent magnetization loops (Figure ). As field dependent magnetization is measured at higher temperatures, we observe the onset of superparamagnetism and eventually weak paramagnetism at 300K along with a diamagnetic background signal from the Si substrate. In order to determine the onset temperature of superparamagnetism, we measure the sample in 500 Oe after it has been cooled in a strong magnetic field of 1T as well as in 500Oe after being cooled in zero magnetic field. Temperature dependences of the field cooled (FC) and zero field cooled (ZFC) magnetization (Figure ) from each other at 12 K, where there is a maximum in the ZFC magnetizations signal. The deviation of the FC and ZFC curves can be correlated with the onset of superparamagnetism and blocking temperature of TB =12 K. Below TB, the ZFC magnetization of nanoparticles is effectively frozen in random orientations, while the FC magnetization of the nanoparticles is aligned. The blocking temperature of 12K observed in the NiB nanoparticles is consistent with other findings that report a blocking temperature of 14K for amorphous NiB nanoparticles . This is well below the transition temperature observed for the CoB core shell nanoparticles, which exhibit a TC above room temperature.