Figure 5
Temperature-dependent conductivities of three Fe 3 O 4 films and a simple theoretical calculation based on the Callaway model. (a, b) Measured thermal conductivities of 100-, 300-, and 400-nm-thick Fe3O4 thin films at temperatures of 20 to 300 K using the 3-ω method, including the thermal conductivity of bulk materials. The solid line denotes thermal conductivity of bulk materials from the theoretical Callaway model, which includes the effect of the impurity, Umklapp process, boundary scattering with film grain size, and film thickness.