A thermally assisted magnetic write head having a near-field transducer, a magnetic lip and a diffusion barrier layer between the near-field transducer and the magnetic lip. The near-field transducer includes a transparent aperture constructed of a material such as SiO2 and an opaque metallic antenna constructed of a metal such as Au formed at a first edge of the aperture. A magnetic lip, connected with the write pole is formed near a second edge of the aperture with a diffusion barrier layer being disposed between the magnetic lip and the aperture. The diffusion barrier layer prevents migration of atomic between the aperture and the magnetic lip, thereby ensuring robust performance at localized high temperatures generated by the near-field transducer.