R&D: Thermal Performance of Materials for HAMR

Journal of Applied Physics has published an article written by Xiaotian Xu, Chi Zhang, Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA, Silu Guo, Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA, Nicholas C. A. Seaton, Characterization Facility, University of Minnesota, Twin Cities, Minneapolis, Minnesota 55455, USA, K. Andre Mkhoyan, Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA, Joseph Roth, Jie Gong, Xuan Zheng, Neil Zuckerman, Seagate Technology LLC, Bloomington 55435, USA, and Xiaojia Wang, Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA.

Abstract: “To increase the storage capacity of hard disk drives, Heat-Assisted Magnetic Recording (HAMR) takes advantage of laser heating to temporarily reduce the coercivity of recording media, enabling the writing of very small data bits on materials with high thermal stability. One key challenge in implementing HAMR is effective thermal management, which requires reliable determination of the thermal properties of HAMR materials over their range of operating temperature. This work reports the thermal properties of dielectric (amorphous silica, amorphous alumina, and AlN), metallic (gold and copper), and magnetic alloy (NiFe and CoFe) thin films used in HAMR heads from room temperature to 500 K measured with time-domain thermoreflectance. Our results show that the thermal conductivities of amorphous silica and alumina films increase with temperature, following the typical trends for amorphous materials. The polycrystalline AlN film exhibits weak thermal anisotropy, and its in-plane and through-plane thermal conductivities decrease with temperature. The measured thermal conductivities of AlN are significantly lower than that which would be present in single-crystal bulk material, and this is attributed to enhanced phonon-boundary scattering and phonon-defect scattering. The gold, copper, NiFe, and CoFe films show little temperature dependence in their thermal conductivities over the same temperature range. The measured thermal conductivities of gold and copper films are explained by the diffuse electron-boundary scattering using an empirical model.“