Structural and magnetic depth profiles of magneto-ionic heterostructures beyond the interface limit

Electric field control of magnetism provides a promising route towards ultralow power information storage and sensor technologies. The effects of magneto-ionic motion have been prominently featured in the modification of interface characteristics. Here, we demonstrate magnetoelectric coupling moderated by voltage-driven oxygen migration beyond the interface in relatively thick AlOx/GdOx/Co(15 nm) films. Oxygen migration and Co magnetization are quantitatively mapped with polarized neutron reflectometry under electro-thermal conditioning. The depth-resolved profiles uniquely identify interfacial and bulk behaviours and a semi-reversible control of the magnetization. Magnetometry measurements suggest changes in the microstructure which disrupt long-range ferromagnetic ordering, resulting in an additional magnetically soft phase. X-ray spectroscopy confirms changes in the Co oxidation state, but not in the Gd, suggesting that the GdOx transmits oxygen but does not source or sink it. These results together provide crucial insight into controlling magnetism via magneto-ionic motion, both at interfaces and throughout the bulk of the films. Mechanisms allowing electrical manipulation of magnetic material possess potential applications in low power memory and sensor technologies. Here, the authors demonstrate the control of magnetic characteristics via voltage-driven migration of oxygen across a GdOx/Co interface, well into the bulk of the cobalt.

[1]  P. A. Seeger,et al.  Resonance effects in neutron scattering lengths of rare-earth nuclides , 1990 .

[2]  Uwe Bauer,et al.  Voltage-controlled domain wall traps in ferromagnetic nanowires. , 2013, Nature nanotechnology.

[3]  J. C. Sloncxewski,et al.  Current-driven excitation of magnetic multilayers , 2003 .

[4]  R. M. Wolf,et al.  Difference between blocking and Néel temperatures in the exchange biased Fe3O4/CoO system. , 2000, Physical review letters.

[5]  I. Mayergoyz.  The Classical Preisach Model of Hysteresis , 1991 .

[6]  Berger.  Emission of spin waves by a magnetic multilayer traversed by a current. , 1996, Physical review. B, Condensed matter.

[7]  J. Borchers,et al.  Reversible Control of Magnetism in La0.67Sr0.33MnO3 through Chemically-Induced Oxygen Migration , 2016 .

[8]  O. Hellwig,et al.  Magnetization reversal of Co/Pt multilayers: Microscopic origin of high-field magnetic irreversibility - eScholarship , 2004 .

[9]  F. Heinrich,et al.  Phase-sensitive specular neutron reflectometry for imaging the nanometer scale composition depth profile of thin-film materials , 2012 .

[10]  H. Tuller,et al.  Electrical and defect thermodynamic properties of nanocrystalline titanium dioxide , 1999 .

[11]  A. Panchula,et al.  Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers , 2004, Nature materials.

[12]  A. Stancu,et al.  What does a first-order reversal curve diagram really mean? A study case: Array of ferromagnetic nanowires , 2013 .

[13]  Uwe Bauer,et al.  Electric field control of domain wall propagation in Pt/Co/GdOx films , 2012 .

[14]  C. Lai,et al.  Probing the A1 to L10 transformation in FeCuPt using the first order reversal curve method , 2014, 1408.2860.

[15]  Kai Liu,et al.  Quantitative Decoding of Interactions in Tunable Nanomagnet Arrays Using First Order Reversal Curves , 2014, Scientific Reports.

[16]  J. Yang,et al.  Memristive switching mechanism for metal/oxide/metal nanodevices. , 2008, Nature nanotechnology.

[17]  Etienne,et al.  Giant magnetoresistance of (001)Fe/(001)Cr magnetic superlattices. , 1988, Physical review letters.

[18]  J. Pedley,et al.  Thermochemical Data for Gaseous Monoxides , 1983 .

[19]  Caroline A. Ross,et al.  First-order reversal curve diagram analysis of a perpendicular nickel nanopillar array , 2005 .

[20]  Ralph,et al.  Current-driven magnetization reversal and spin-wave excitations in Co /Cu /Co pillars , 1999, Physical review letters.

[21]  V. F. Sears.  Neutron scattering lengths and cross sections , 1992 .

[22]  J. Hirsch.  Spin Hall Effect , 1999, cond-mat/9906160.

[23]  A. Vega,et al.  Structure, fragmentation patterns, and magnetic properties of small nickel oxide clusters. , 2014, Physical chemistry chemical physics : PCCP.

[24]  R. Williams,et al.  Exponential ionic drift: fast switching and low volatility of thin-film memristors , 2009 .

[25]  E. Seymann,et al.  Neutron scattering lengths: A survey of experimental data and methods , 1991 .

[26]  Jia-ling Wang,et al.  Density functional calculations for structural, electronic, and magnetic properties of gadolinium-oxide clusters , 2014 .

[27]  H. Ohno,et al.  Electric-field control of ferromagnetism , 2000, Nature.

[28]  S. Satija,et al.  Determination of the effective transverse coherence of the neutron wave packet as employed in reflectivity investigations of condensed-matter structures. I. Measurements , 2014, 1403.3646.

[29]  Charles F. Majkrzak,et al.  Polarized neutron reflectometry , 1991 .

[30]  Stuart A. Wolf,et al.  Spintronics : A Spin-Based Electronics Vision for the Future , 2009 .

[31]  Binasch,et al.  Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange. , 1989, Physical review. B, Condensed matter.

[32]  J. Borchers,et al.  Vertically graded anisotropy in Co/Pd multilayers , 2009, 0912.0256.

[33]  J Joshua Yang,et al.  Memristive devices for computing. , 2013, Nature nanotechnology.

[34]  Shufeng Zhang,et al.  Reversible control of Co magnetism by voltage-induced oxidation. , 2014, Physical review letters.

[35]  W. M. Haynes.  CRC Handbook of Chemistry and Physics , 1990 .

[36]  M D Rossell,et al.  Reversible electric control of exchange bias in a multiferroic field-effect device. , 2010, Nature materials.

[37]  J. Stöhr,et al.  Parallel versus antiparallel interfacial coupling in exchange biased Co/FeF2. , 2006, Physical review letters.

[38]  Shan X. Wang,et al.  Electric-field control of local ferromagnetism using a magnetoelectric multiferroic. , 2008, Nature materials.

[39]  Mayergoyz,et al.  Mathematical models of hysteresis. , 1986, Physical review letters.

[40]  S. Yuasa,et al.  Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions , 2004, Nature materials.

[41]  Starke,et al.  Magnetic circular dichroism in core-level photoemission from Gd, Tb, and Dy in ferromagnetic materials. , 1995, Physical review. B, Condensed matter.

[42]  H. Tompkins,et al.  The oxidation of cobalt in air from room temperature to 467°C , 1981 .

[43]  Uwe Bauer,et al.  Magneto-ionic control of interfacial magnetism. , 2014, Nature materials.

[44]  A. Marty,et al.  Electric Field-Induced Modification of Magnetism in Thin-Film Ferromagnets , 2007, Science.

[45]  D. Pierce,et al.  Realization of ground-state artificial skyrmion lattices at room temperature , 2015, Nature Communications.

[46]  Dario Manara,et al.  The Thermodynamic Properties of the f-Elements and their Compounds. Part 2. The Lanthanide and Actinide Oxides , 2014 .

[47]  C. R. Pike.  First-order reversal-curve diagrams and reversible magnetization , 2003 .

[48]  J. Borchers,et al.  Controllable positive exchange bias via redox-driven oxygen migration , 2016, Nature Communications.

[49]  Christian Stamm,et al.  Chemical effects at metal/oxide interfaces studied by x-ray-absorption spectroscopy , 2001 .

[50]  D. Ralph,et al.  Spin-Torque Switching with the Giant Spin Hall Effect of Tantalum , 2012, Science.