Effect of surface roughness on the anomalous Hall effect in Fe thin films

Surface roughness plays an important role on the magnetotransport properties of thin films, especially in ultrathin films. In this work, we prepared Fe thin films with various surface roughness by using different seed layers and studied the electrical transport and anomalous Hall effect. By tuning surface roughness scattering, the longitudinal resistivity (${\rho }_{xx}$) measured at 5 K increases by one order of magnitude and the corresponding anomalous Hall resistivity (${\rho }_{\mathrm{AHE}}$) increases by three times with increasing roughness. The intrinsic, skew-scattering, and side-jump contributions to ${\rho }_{\mathrm{AHE}}$ were separated from our data. The anomalous Hall angle depends on the surface roughness, which may be of importance to the material engineering for achieving large spin Hall angle.

Figure 1

HRTEM images of cross-sections of the samples (a) Ta/Fe and (b) Cu/Fe. (c) GID spectra for all samples.

Figure 2

(a) Temperature-dependent longitudinal resistivity (${\rho }_{xx}$) curves for all samples. (b) Normalized ${\rho }_{xx}\left(T\right)/{\rho }_{xx}\left(300\mathrm{K}\right)\sim T$ curves for all samples.

Figure 3

(a) Field-dependent Hall resistivity (${\rho }_{xy}$) of all samples measured at 5 K. (b) Temperature-dependent anomalous Hall resistivity (${\rho }_{\mathrm{AHE}}$) for all samples.

Figure 4

(a) Anomalous Hall resistivity (${\rho }_{\mathrm{AHE}0}$) vs longitudinal resistivity (${\rho }_{xx0}$) at 5 K. The solid line is a guide to eyes. (b) Intrinsic anomalous Hall conductivity ($b$) as a function of ${\rho }_{xx0}$. The inset shows the linear dependence of $b$ on ${\sigma }_{xx0}$. (c) Extrinsic anomalous Hall resistivity as a function of ${\rho }_{xx0}$. The solid line is a fitting curve by Eq. (7). The same set of data shown in the inset was fitted by Eq. (3). (d) The anomalous Hall angle (${\rho }_{\mathrm{AHE}0}$/${\rho }_{xx0}$) at 5 K vs ${\rho }_{xx0}$.

Figure 5

(a) Normalized ${\rho }_{xx}\left(T\right)/{\rho }_{xx}\left(300\mathrm{K}\right)\sim T$ curves for the samples listed in the legend. The legend is the same in (b) and (c). (b) Field-dependent Hall resistivity measured at 5 K. (c) Temperature-dependent ${\rho }_{\mathrm{AHE}}$ for the samples.