Iron Composition Dependence of Longitudinal Spin Seebeck Voltage in Co_3-XFe_XO₄ Films Prepared by Chemical Processes

Abstract

  We investigate the dependence of the structure, magnetic properties, and longitudinal spin Seebeck effect (LSSE) voltage on the Fe composition (X) in Co_3-XFe_XO₄ (CFO) films prepared via co-precipitation and spin-coating on a Si substrate, where X is varied from 0.53 to 1.98. The crystal structure of the CFO films shows the spinel structure, whereas the Lotgering factor, which is related to the orientation distribution of crystal-oriented polycrystallines, indicates the maximum values at 0.72 ≤ X ≤ 1.17 and decreases at 1.38 ≤ X ≤ 1.98. The saturation magnetization (M_S) and effective anisotropy of the CFO films increase with X. The LSSE constant (S) of the CFO films increases with increasing X, and the maximum value of |S| is 5.9 × 10^-3 μV K^-1 at X = 1.81. The trend in |S| with increasing X is attributed to the enhancement of M_S which affects the magnon density, and to the reduction of thermal conductivity which affects the temperature gradient.