Clear evidence of interfacial anomalous Hall effect in epitaxial L10 FePt and FePd films

Abstract

Anomalous Hall effect in epitaxially grown $L{1}_{0}$-ordered FePd and FePt films on MgO(001) has been investigated as a function of the film thickness ($d$). It is found that the anomalous Hall resistivity can be described by conventional scaling law, i.e., ${\ensuremath{\rho}}_{\mathrm{AH}}=a{\ensuremath{\rho}}_{xx}+b{\ensuremath{\rho}}_{xx}^{2}$ with longitudinal resistivity ${\ensuremath{\rho}}_{xx}$. It is interesting to find that both $a$ and $b$ parameters approximately change as a linear function of the inverse film thickness. The linear $1/d$ dependencies can be attributed to the symmetry breaking at the surface. Moreover, the bulk and in particular the surface contributions to the parameters $a$ and $b$ in $L{1}_{0}$ FePt films are enhanced, compared with those of $L{1}_{0}$ FePd films, due to larger spin orbit interaction of heavier Pt atoms. It is indicated that not only the bulk but also the interface components of $a$ and $b$ are tuned by the spin-orbit interaction. The present results might stimulate further theoretical investigation of the mechanism of the anomalous Hall effect.