Three　kinds　of　spinel　ferrite　nanocrystals,　MFe2O4　(M　=　Co,　Ni,　and　Mn),　are　synthesized　using　colloid　mill　and　hydrothermal　method.　During　the　synthesis　process,　a　rapid　mixing　and　reduction　of　cations　with　sodium　borohydride　(NaBH4)　take　place　in　a　colloid　mill　then　through　a　hydrothermal　reaction,　a　slow　oxidation　and　structural　transformation　of　the　spinel　ferrite　nanocrystals　occur.　The　phase　purity　and　crystal　lattice　parameters　are　estimated　by　X-ray　diffraction　studies.　Scanning　electron　microscopy　and　transmission　electron　microscopy　images　show　the　morphology　and　particle　size　of　the　as-synthesized　ferrite　nanocrystals.　Raman　spectrum　reveals　active　phonon　modes　at　room　temperature,　and　a　shifting　of　the　modes　implies　cation　redistribution　in　the　tetrahedral　and　octahedral　sites.　Magnetic　measurements　show　that　all　the　obtained　samples　exhibit　higher　saturation　magnetization　(M-s).　Meanwhile,　experiments　demonstrate　that　the　hydrothermal　reaction　time　has　significant　effects　on　microstructure,　morphologies,　and　magnetic　properties　of　the　as-synthesized　ferrite　nanocrystals.　(C)　2015　Author(s).　All　article　content,　except　where　otherwise　noted,　is　licensed　under　a　Creative　Commons　Attribution　3.0　Unported　License.