Boundary Magnetization and Exchange Bias of Boron Doped Cr$_{2}$O$_{3}$ Pinning Layers*

This research is part of an effort to utilize voltage-controlled boundary magnetization (BM) in the magnetoelectric (ME) Cr$_{2}$O$_{3}$ for spintronic applications. We exploit the electric switchable boundary magnetic moment (MM) of Cr$_{2}$O$_{3}$. The net MM at the interface can be useful to manipulate the magnetic states of an adjacent ferromagnetic (FM) material. Using a FM Pd/Co multilayer deposited on Cr$_{2}$O$_{3}$, reversible, room-temperature isothermal switching of the exchange bias field has been achieved by reversing the electric field. The voltage-controlled magnetization of the FM layer can be utilized as a state variable. However, to use voltage-controlled BM as a key spintronic material for devices operating at room temperature, the N\'{e}el temperature $T_{N}$ of the ME antiferromagnet must be increased above the bulk value of $T_{N} =$307 K of pure Cr$_{2}$O$_{3}$. First principles calculations show that boron doping of Cr$_{2}$O$_{3}$ can increase $T_{N}$. We diagram structural and magnetic characterizations of pure and B-Cr$_{2}$O$_{3}$ grown on Al$_{2}$O$_{3}$. An increase in $T_{N}$ of 120 K is achieved making Cr$_{2}$O$_{3}$ suitable for room temperature spintronic applications. Further, we attempt to create an exchange bias (EB) system using a FM Pd/Co multilayer on B-doped Cr$_{2}$O$_{3}$. From this, we attempt to switch the EB field via the electric field.