R&D: Optical Forces in HAMR Head-Disk Interface

Scientific Reports has published an article written by Roshan Mathew Tom, Department of Mechanical Engineering, UC Berkeley, Berkeley, CA, 94720, USA, Robert Smith, Oscar Ruiz, Qing Dai, The CTO Office, Western Digital Technologies, San Jose, CA, 95119, USA, and David B. Bogy, Department of Mechanical Engineering, UC Berkeley, Berkeley, CA, 94720, USA.

Abstract: “A main challenge in Heat-Assisted Magnetic Recording technology is the build-up of contaminants called smear on the near field transducer. In this paper, we investigate the role of optical forces originating from the electric field gradient in the formation of smear. First, based on suitable theoretical approximations, we compare this force with air drag and the thermophoretic force in the head-disk interface for two smear nanoparticle shapes. Then, we evaluate the force field’s sensitivity to the relevant parameter space. We find that the smear nanoparticle’s refractive index, shape, and volume significantly impact the optical force. Further, our simulations reveal that the interface conditions, such as spacing and the presence of other contaminants, also influence the magnitude of the force.“