Magnetic Properties of Epitaxial Cr/Cr$_{2}$O$_{3}$/ Cr Multilayers

We study Cr/Cr$_{2}$O$_{3}$/Cr trilayer structures grown by Molecular Beam Epitaxy on (111) oriented Al$_{2}$O$_{3 }$substrates. X-ray diffraction reveals perfect single crystalline (110) Cr and stoichiometric single crystalline Cr$_{2}$O$_{3}$ (111) films. Both, Cr and Cr$_{2}$O$_{3 }$order antiferromagnetically with bulk N\'{e}el temperatures of 311 and 307K, respectively. Cr is an itinerant antiferromagnet where the antiferromagnetic (AF) order establishes as an incommensurate spin density wave. Cr$_{2}$O$_{3 }$in contrast is an AF insulator with localized magnetic moments where magnetoelectric and piezomagnetic effects are both symmetry allowed. Its insulating, magnetoelectric and piezoelectric properties make Cr$_{2}$O$_{3}$ an interesting material for extrinsically controlled tunnel barriers in TMR type structures. The lattice mismatch of $\sim $1.2{\%} at the Cr -- Cr$_{2}$O$_{3}$ interface creates a strong stress induced piezomagnetic moment revealed by SQUID measurements. The interaction between the piezomoment and the spin distribution at the Cr- interface gives rise to a rich scenario of magnetic proximity effects which we study by SQUID magnetometry, magneto-optical Kerr effect and electrical transport measurements.