Temperature sensitive ferrofluid has been prepared by dispersing oleic acid modified Mn1 - xZnxFe2O4 nanopartides into hydrocarbon based carriers. Mn1 - xZnxFe2O4 nanoparticles with good crystalline quality and magnetic properties were synthesized by a novel modified hydrothermal process with purification of precursor. Crystalline and magnetic properties of Mn1 - xZnxFe2O4 particles with different x were discussed. Mn1 - xZnxFe2O4 particles show a high saturation magnetization up to 54.6 emu/g and low Curie points (T-c, most are below 100 degrees C). Sharp magnetic-temperature gradients are observed at T-c for all samples with different Zn content (13.0 emu/g/K in the case of Mn0.5Zn0.5Fe2O4). The excellent magnetic properties are proposed to be the results of distribution of cations at special sites and the good quality of products including good crystallization, fine size and uniformity of obtained particles. (C) 2011 Elsevier B.V. All rights reserved.