Manganese zinc iron and zinc gadolinium iron magnetic nanoparticles were synthesized by chemical methods and by co-precipitation process. The particles were further encapsulated with a biodegradable polymer, PEG. The particles have a Curie temperature (Tc) in the range of 43-46°C and are designed to be used for magnetic hyperthermia application, one of the many therapy options for cancer treatment. Morphology and magnetic properties of these encapsulated nanoparticles were determined by TEM, XRD and SQUID. Curie temperatures for the alloy particles and encapsulated particles were also measured. The AC magnetic heating pattern of particles at ̃ 961 KHz using alcohol thermometer is presented. The frequency dependence of the heating follows general trends predicted by power loss equations and is similar to traditional materials. In conclusion, quality heating particles were synthesized and shown to generate sufficient heating at room temperature and self-controlled by their respective Curie temperatures.