RESUMO
Voltage-controlled magnetic anisotropy (VCMA) in an epitaxially grown Fe/Fe1-xCox/Pd/MgO system was investigated using spin-wave spectroscopy. The spin-wave resonant frequency linearly depended on the bias-voltage. The resonant-frequency shift increased with the Co fraction in Fe1-xCox/Pd. We achieved a VCMA of approximately 250 fJ/Vm at the Co/Pd/MgO region.
RESUMO
Electric fields at interfaces exhibit useful phenomena, such as switching functions in transistors, through electron accumulations and/or electric dipole inductions. We find one potentially unique situation in a metal-dielectric interface in which the electric field is atomically inhomogeneous because of the strong electrostatic screening effect in metals. Such electric fields enable us to access electric quadrupoles of the electron shell. Here we show, by synchrotron X-ray absorption spectroscopy, electric field induction of magnetic dipole moments in a platinum monatomic layer placed on ferromagnetic iron. Our theoretical analysis indicates that electric quadrupole induction produces magnetic dipole moments and provides a large magnetic anisotropy change. In contrast with the inability of current designs to offer ultrahigh-density memory devices using electric-field-induced spin control, our findings enable a material design showing more than ten times larger anisotropy energy change for such a use and highlight a path in electric-field control of condensed matter.
