Linearity in perpendicular magnetic recording was studied. An asymmetrical transition-shift occurs depending on the polarity of the pre-recorded magnetization of a medium, which deteriorates linearity. A new single pole head with two main poles which we cab the bi-layered head improved linearity by avoiding the interference of magnetic Field From the magnetized medium with the head Field, As a result, 200 kFRPI recording was demonstrated to be practical with the partial response technique.