Quadrupole modulation in magnetic anisotropy in Fe3Si film on Pb(Mg1/3Nb2/3)O3–PbTiO3 under reversible strain

We investigate the microscopic origins of magnetic anisotropy in the ferromagnetic binary alloy Fe3Si film while applying reversible strain on a ferroelectric Pb(Mg,Nb)O3–PbTiO3 substrate. X-ray magnetic circular dichroism with the introduction of reversible strain clearly demonstrates the change in the magnetic easy axis direction, even with an anisotropy energy of 1.6 × 103 J/m3. The strain-dependent Mössbauer spectroscopy detects changes in the quadrupole shift, which are related to variations in the electric field gradient from the valence electron distribution. The density-functional-theory calculation also supports the electron quadrupole contribution to magnetic anisotropy. These results indicate that the strain-dependent changes in the magnetic easy axis in Fe3Si arise from the formation of the charge quadrupole at the strained Fe sites. This characteristic is notably different from that of the ferromagnetic Heusler alloy Co2FeSi, where one of the Fe sites in Fe3Si are replaced by Co. This study provides a significant approach to understanding and designing interfacial multiferroic materials.