Perpendicular magnetic recording medium with metamagnetic antiferromagnetically-coupled layer between the soft underlayer and recording layer

Abstract

A perpendicular magnetic recording medium includes a metamagnetic antiferromagnetically-coupled (AFC) layer between the recording layer (RL) and the soft magnetically permeable underlayer (SUL). The metamagnetic AFC layer has essentially no net magnetic moment in the absence of a magnetic field, but is highly ferromagnetic in the presence of a magnetic field above a threshold field. Thus the metamagnetic AFC layer does not contribute to the readback signal during reading, but channels the write field to the SUL during writing because the threshold field is selected to be below the write field. An exchange-break layer EBL is located between the metamagnetic AFC layer and the RL. The metamagnetic AFC layer contains films with a crystalline structure suitable as a growth template for the EBL and RL, so the metamagnetic AFC layer also functions as part of an 'effective EBL', thereby allowing the actual EBL to be made as thin as possible.