A series of experiments have been designed to explore the upper limits in properties that can be produced from the high pressure, high temperature process for the synthesis of ferro-magnetic chromium dioxide. These show that CrO2coercivity and surface area, i.e. particle size, can be controlled independently over a wide range by the selection of the Cr3+to Cr6+ratio and type and level of dopant. Examples of high coercivity, reduced aspect ratio and high surface area are discussed. The performance of the high surface area (37 m2/g) in consumer video media is presented. Along with these results, a methodology that separates the particle contribution to media performance from the tape process parameters, such as surface smoothness, is presented.