Measurement of thermal conductivities of SiN and TbFeCo films

The effective thermal conductivities of SiN and TbFeCo thin films were measured by comparing the length and width of a polarizing microscope image of thermo-magnetically written domains with those of calculated isotherms for the trilayer structure of substrate/Si/sub 3/N/sub 4//Tb/sub 22/Fe/sub 70/Co/sub 8//Si/sub 3/N/sub 4/. The resulting data were applied to the quadrilayer structure of substrate/Si/sub 3/N/sub 4//Tb/sub 22/Fe/sub 70/Co/sub 8//Si/sub 3/N/sub 4//Al, and the length of the calculated isotherms turned out to agree with that of the written domain.