Determining the planar Nernst effect from magnetic-field-dependent thermopower and resistance in nickel and permalloy thin films

Abstract

We present magnetic-field-dependent measurements of thermopower, $\ensuremath{\alpha}$(H), and resistance, $R(H)$, for ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ and Ni thin films. We conducted these experiments in fields oriented parallel and perpendicular to the applied thermal gradient, $\stackrel{P\vec}{\ensuremath{\nabla}}T$, for $\ensuremath{\alpha}$(H) and applied current for $R(H)$. We deposited the 20-nm-thick films on 500-nm-thick suspended Si-N thermal isolation platforms that enable in-plane measurements of thermal and electrical properties of thin films. Both $\ensuremath{\alpha}(H)$ and $R(H)$ in Ni-Fe and Ni films exhibit evidence of spin-dependent scattering through an even field dependence and a linear proportionality between $\ensuremath{\alpha}(H)$ and $1/R(H)$. Finally, we use $\ensuremath{\alpha}({\mathrm{H}}_{\ensuremath{\parallel}})$ and $\ensuremath{\alpha}({\mathrm{H}}_{\ensuremath{\perp}})$ to determine the planar Nernst coefficient in Ni-Fe and Ni thin films and use this coefficient to predict the size of the planar Nernst effect (PNE) in the micromachined platform. The measured field dependence of the PNE is well matched by the prediction obtained from our $\ensuremath{\alpha}$(H) results.