Low Temperature Scaling of the Susceptibility of Ni Films...

Measurement of low field ac susceptibility of Ni thin films over the temperature range 5-300K reveals a surprising power law scaling. The temperature dependent part of the normalized susceptibility, $\chi_\parallel/M_S-\chi_{\rm rot}/M_S$, where $\chi_\parallel$ is the initial susceptibility for in-plane magnetization, $\chi_{\rm rot}$ is the domain rotation contribution, and $M_S$ is the saturation magnetization, scales with the nonlinear reduced temperature as $t^{-2}$ over the entire temperature range, where $t=(T-T_C)/(T+T_C)$ and $T_C$ is the Curie temperature. Thickness and reduced temperature dependences are completely decoupled. This result implies that domain wall motion does not contribute to the low field susceptibility.