Rheological characterizations were made for various types of magnetic particles (rod-like gamma-Fe2O3, CrO2, and plate-like Ba-ferrite) and nonmagnetic (rod-like alpha-Fe2O3) suspensions, in terms of particle concentration and shear rate. Shear rate dependence on viscosity was accurately described by the Casson equation. The highest yield stress for Ba-ferrite among the four types of particles represents the sensitive flocculation characteristics of Ba-ferrite with respect to concentration. The effect of non-magnetic alpha-Fe2O3 and magnetic gamma-Fe2O3 particle mixtures on suspension viscosity was also examined, and a negative deviation from the tie line of individual particle viscosities was observed.