A write portion for a thermally assisted magnetic head slider includes an air bearing surface facing to a magnetic recording medium; a write element having an opposed-to-magnetic recording medium surface; a waveguide for guiding light generated by a light source module mounted on a substrate of the thermally assisted magnetic head slider; and a plasmon unit provided around the write element, which has a near-field light generating surface for propagating near-field light to the air bearing surface. And only the opposed-to-magnetic recording medium surface of the write element is covered by a carbon layer. The invention can prevent corrosive elements in the write portion from being corroded and prevent the write element from being worn and abraded not only, and maintain stable thermal ability for a plasmon unit but also.