Effect of electric field doping on the anisotropic magnetoresistance in doped manganites

Abstract

We have modulated the anisotropic magnetoresistance (AMR) in $3--4\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ manganite films using the ferroelectric field effect---a method that electrostatically varies the carrier density without affecting the lattice distortion. While significant changes have been induced in ${T}_{C}$ and $\ensuremath{\rho}$, the AMR ratio remains the same when the magnetic state is not changed. This scaling behavior is in striking contrast to chemical doping results, where similar modulation of the carrier concentration $(\ensuremath{\sim}0.1∕\mathrm{Mn})$ changes the AMR ratio by $\ensuremath{\geqslant}30%$. The results reveal unambiguously the dominant role of chemical distortion in determining the AMR in manganites.