Manganese doped ferrite (MnxFe3-xO4) nanoparticles with x = 0.29-0.77, were prepared under solvothermal conditions in the presence solely of a polyol using the trivalent manganese and iron acetylacetonates as precursors. In this facile approach, a variety of polyols such as, polyethylene glycol (PEG 8000), tetraethylene glycol (TEG), propylene glycol (PG) and a mixture of TEG and PG (1:1) were utilized in a triple role as solvent, reducing and surface-functionalizing agent. Composition of the fine cubic-spinel structures, found in proportion to the reductive ability of each polyol, while determination of structural characteristics plus the inversion parameter (i=0.18-0.38), were provided by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies at both the Fe and Mn K-edges. The saturation magnetization increased up to 80 emu/g when x = 0.35 and i = 0.22. In addition, the as-prepared nanocrystals coated with PEG, PG and PG & TEG showed excellent colloidal stability in water, while hydrophilic properties arisen from the TEG-coated particles when were extra PEGylated. Measurements of the 1H NMR relaxation in water were carried out and the nanoprobes were evaluated as potential contrast agents.