Electric-field control of magnetization in Co$_{40}$Fe$_{40}$B$_{20 }$/ Pb(Mg$_{1/3}$Nb$_{2/3})_{0.7}$Ti$_{0.3}$O$_{3}$ structure at room temperature*

Electric-field control of magnetization is important for new generation information storage technology with high integration density and low power consumption. A lot of work has been carried out on electric-field control of magnetization in artificial ferromagnetic-ferroelectric (FM-FE) two-phase systems via the piezo-strain effect. Beside strain, electric/elastic domains and phase structure also play important roles in the electric-field control of magnetization, especially in the case of amorphous FM film without magnetocrystalline anisotropy. We report a large magnetoelectric effect in a Co$_{40}$Fe$_{40}$B$_{20}$/Pb(Mg$_{1/3}$Nb$_{2/3})_{0.7}$Ti$_{0.3}$O$_{3}$ structure at room temperature. Investigations on the ferroelectric domains, phase structures, magnetic domains and strain with \textit{in situ} electric fields reveal a new mechanism for electric-field control of magnetization. This work provides a new way to realize large magnetoelectric coupling and is significant for applications, especially in the field of CoFeB-based spin valves to achieve electric-controlled magnetic random access memories.