POWDER FOR SUBLAYER OF COATING TYPE MAGNETIC RECORDING MEDIUM AND MAGNETIC RECORDING MEDIUM COMPRISI

A powder for an underlayer of a coating-type magnetic recording medium comprises acicular iron oxide particles having an average major axis length in the range of 20 - 200 nm, has a specific surface area measured by the BET method of 30 - 100 m2/g and has a powder pH of not greater than 7. The underlayer powder preferably contains 0.1 - 5.0 wt% of P and optionally contains an amount of R (where R represents one or more rare earth elements, defined as including Y) such that R/Fe expressed in atomic percentage (at.%) is 0.1 - 10 at.%. The iron oxide powder enhances the properties required of a powder for forming the underlayer of a multi-layer structure coating-type magnetic recording tape, most notably the surface smoothness and strength of the tape.