Nanoscale Heating of the Near Field Transducer in Heat Assisted Magnetic Recording

Current heat assistance magnetic recording hard disk drive systems are designed to heat a 20 nm writing spot on the disk to more than 400 °C by a near field transducer (NFT) located within the slider and spaced a few nanometers from the disk. It is important for the NFT to remain relatively cool to insure that it will not fail during the required lifetime of the drive. Due to the nanometer scale separation between the heated spot and the NFT, the heat exchange between them cannot be accurately calculated by conventional methods. This paper first explains why the conventional models of heat transfer fail at the nanoscale. Then, we estimate the heat radiation and heat conduction due to phonon tunneling using an extension of Planck´s law from equilibrium systems to systems with a non-vanishing heat flux. It is shown that the heat transport across a few nanometers wide gap is expected to be high enough to provide significant back-heating of the NFT from the heated spot on the disk.