Perovskite-type cobalt oxide at the multiferroic Co/Pb Zr$_{0.2}$Ti$_{0.8}$O$_{3}$ interface

K. Mohseni; A. Polyakov; H. B. Vasili; I. V. Maznichenko; S. Ostanin; A. Quindeau; N. Jedrecy; E. Fonda; L. V. Bekenov; V. N. Antonov; P. Gargani; M. Valvidares; I. Mertig; S. S. P. Parkin; A. Ernst; H. L. Meyerheim

arXiv · 2004.00489

Perovskite-type cobalt oxide at the multiferroic Co/Pb Zr$_{0.2}$Ti$_{0.8}$O$_{3}$ interface

K. Mohseni·A. Polyakov·H. B. Vasili·I. V. Maznichenko·S. Ostanin·A. Quindeau·N. Jedrecy·E. Fonda·L. V. Bekenov·V. N. Antonov·P. Gargani·M. Valvidares·I. Mertig·S. S. P. Parkin·A. Ernst·H. L. Meyerheim

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Abstract

Magnetic Tunnel Junctions whose basic element consists of two ferromagnetic electrodes separated by an insulating non-magnetic barrier have become intensely studied and used in non-volatile spintronic devices. Since ballistic tunnel of spin-polarized electrons sensitively depends on the chemical composition and the atomic geometry of the lead/barrier interfaces their proper design is a key issue for achieving the required functionality of the devices such as e.g. a high tunnel magneto resistance. An important leap in the development of novel spintronic devices is to replace the insulating barrier by a ferroelectric which adds new additional functionality induced by the polarization direction in the barrier giving rise to the tunnel electro resistance (TER). The multiferroic tunnel junction Co/PbZr$_{0.2}$Ti$_{0.8}$O$_{3}$/La$_{2/3}$Sr$_{1/3}$MnO$_3$ (Co/PZT/LSMO) represents an archetype system for which - despite intense studies - no consensus exists for the interface geometry and their effect on transport properties. Here we provide the first analysis of the Co/PZT interface at the atomic scale using complementary techniques, namely x-ray diffraction and extended x-ray absorption fine structure in combination with x-ray magnetic circular dichroism and ab-initio calculations. The Co/PZT interface consists of one perovskite-type cobalt oxide unit cell [CoO$_{2}$/CoO/Ti(Zr)O$_{2}$] on which a locally ordered cobalt film grows. Magnetic moments (m) of cobalt lie in the range between m=2.3 and m=2.7$\mu_{B}$, while for the interfacial titanium atoms they are small (m=+0.005 $\mu_{B}$) and parallel to cobalt which is attributed to the presence of the cobalt-oxide interface layers. These insights into the atomistic relation between interface and magnetic properties is expected to pave the way for future high TER devices.

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K. Mohseni, A. Polyakov, H. B. Vasili, I. V. Maznichenko, S. Ostanin, A. Quindeau, N. Jedrecy, E. Fonda, L. V. Bekenov, V. N. Antonov, P. Gargani, M. Valvidares, I. Mertig, S. S. P. Parkin, A. Ernst, H. L. Meyerheim. 2020-04-01. Perovskite-type cobalt oxide at the multiferroic Co/Pb Zr$_{0.2}$Ti$_{0.8}$O$_{3}$ interface. https://arxiv.org/abs/2004.00489

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