SYMPOSIUM H Functional and Multifunctional Oxide Films November 29 - December 3, 2004 Chairs Chang-Beom Eom Darrell G. Schlom Dept. of Materials Science & Engineering Dept. of Materials Science & Engineering University of Wisconsin-Madison Pennsylvania State University Rm. 2164 ECB 108 Materials Research Inst. Bldg 1550 Engineering Dr. University Park, PA 16802-6602 Madison, WI 53706 814-863-8579 608-263-6305 Jean-Marc Triscone David Norton DPMC Dept. of Materials Science & Engineering University of Geneva University of Florida 24 Quai E.-Ansermet 106 Rhines Hall 1211 Geneva, 4 Switzerland Gainesville, FL 32611-6400 41-22-379-6827 352-846-0525 Symposium Support Swiss National Centre of Competence in Research Materials with Novel Electronic Properties - MaNEP * Invited paper 196 SESSION HI: Multiferroics 9:30 AM H1.4 Chairs: Chang-Beom Eom and Karin Rabe Multiferroic BiFe03 Thin Films. Junling Wang', Haimei Zheng', Monday Morning, November 29, 2004 Manfred Wuttig', Jiefang Li2, Feiming Bai2 , Dwight Viehland2 and Grand Ballroom (Sheraton) R. Ramesh3; lDepartment of Materials Science and Engineering, University of Maryland, College Park, Maryland; 2Department of 8:15 AM *H1.1 Materials Science and Engineering, Virginia Tech, Blacksburg, Computational Design of Multifunctional Oxides. Virginia; 3Department of Materials Science and Engineering, Nicola A. Spaldin, Pio Baettig and Claude Ederer; Materials University of California, Berkeley, California. Department, University of California, Santa Barbara, California. Multiferroic materials have attracted many research activities recently. In this talk we show how modern theoretical and computational Among all the choices, BiFe03 is of particular interests because of its methods can be used to design technologically relevant oxides with simple structure and the coexistence of ferroelectric (Te 1100K) and dual- or multi-functionality. We choose multiferroic magnetoelectrics antiferromagnetic (TN 640K) orders at room temperature. Properties as an example; these are materials that are both ferromagnetic and of BiFe03 have been puzzling. (1) Reported polarization value « ferroelectric in the same phase, and therefore have a spontaneous 10!,C/cm2) is very small for a ferroelectric material with such a high magnetization which can be switched by an applied magnetic field, a Curie temperature. (2) Its G-type antiferromagnetic spin spontaneous polarization which can be switched by an applied electric configuration is subjected to a spiral modulation. We have field, and often some coupling between the two. Very few exist in successfully deposited highly resistive BiFe03 thin films using pulsed nature, or have been synthesized in the laboratory, so we begin by laser deposition. (001), (110) and (111) cut SrTi03 substrates were determining the reason for the scarcity of ferromagnetic ferroelectric used to control the film orientation. Much larger polarizations were coexistence. Then we identify the chemistry behind the additional observed for all three orientations ( 55 !,C/cm2 for (001) films, 80 electronic or structural driving forces that must be present for !,C/cm2 for (101) films, and 100 !,C/cm2 for (111) films). We will ferromagnetism and ferroelectricity to occur simultaneously. Finally also report our results on the dielectric and piezoelectric responses we describe the successful prediction and subsequent synthesis of new along the different crystallographic directions, as well as the field and multiferroics and discuss the limitations that fundamental physics temperature dependence magnetic property characterized by SQUID. imposes on their potential applications. This work is supported by the Office of Naval Research (grant #s, MURI N000140110761, N000140210340, N000140210126) and the 8:45 AM *H1.2 National Science Foundation (grant #s MRSEC DMR-00-80008). Nonlinear Optical Probing of Ferroic and Multiferroic Complex Oxide Thin Films. Venkatraman Gopalan', Alok 10:15 AM H1.5 Sharanl , Aravind Vasudevaraol , Yulan Lil , Long-qing Chenl , Darrell Giant Ferroelectric Polarization in Multiferroic BiFe03 Thin l Schlom', J. Schubert3 , K. J. Choi2, Chang-Beom Eom2 , R. Uecker4 Films. Kwi-Young Yun , Dan Ricinschi l, Minoru Nodal, Saburo 4 En~ineering, and P. Reiche ; 1 Materials Science and Penn State Nasu2 and Masanori Okuyamal ; lDepartment of Systems Innovation, University, University Park, Pennsylvania; Department of Materials Osaka University, Osaka, Japan; 2Department of Physical Science, Science and Engineering, University of Wisconsin-Madison, Madison, Osaka University, Osaka, Japan. Wisconsin; 3Institut fur Schichten und Grenzfiachen ISG I-IT, Forschungszentrum Julich GmbH, Julich, Germany; 4Institute of Bismuth ferrite (BiFeO 3, BFO) has attracted considerable interest Crystal Growth, Berlin, Germany. recently due to its giant ferroelectric polarization (GFP) and multiferroic properties (simultaneously exhibiting ferroelectric and Ferroic and multiferroic materials have a rich array of cross-coupled magnetic ordering). Prepared in thin film form, it has shown a much phenomena ranging from ferroelectricity, ferromagnetism, larger remanent polarization than that in bulk. This was attributed to ferroelasticity, piezoelectricity, pyroelectricity, magnetoelectricity, the high sensitivity of polarization to small changes of the crystalline piezomagnetism, electro-optic, magneto-optic, elasto-optic and structure and lattice parameters of the film heteroepitaxially nonlinear optical effects. In thin film form, complex domain constrained to the single crystal substrate. The 300nm-thick BFO thin microstructures, their dynamics, and phase transitions can be a films have been deposited on Pt/Ti02 /Si02 /Si substrates by PLD. challenge to study, particularly when direct electrical measurements The oxygen pressure was 0.05 Torr and the deposition temperature are not feasible due to dielectric losses, and structural distinctions was fixed at 450°C. Pt top electrodes with 240 !'m diameter have between domain variants is too small to detect through conventional been formed by rf-sputtering. The room-temperature (RT) X-ray means. This talk presents nonlinear optical probing, particularly diffraction measurement indicates that the BFO thin films grown on through second harmonic generation, as a powerful quantitative means Pt/Ti02/Si02 /Si substrate consist of polycrystalline perovskite of of probing complex domain dynamics in real time under external single-phase with the lattice parameters of a = 0.393 and c = 0.400 influences such as electric fields and temperature. Specific example nm. Ferroelectric polarization vs. electric field (P - E) hysteresis loop systems of epitaxially strained ferrelectric systems of BaTi03 and of BFO thin film was measured in 1 kHz triangular waveform at SrTi03 with giant ferroelectric enhancement, and ferroelectricity in various temperatures of 90 K to RT. The remanent polarization (Pr ) multiferroic system of BiMn03 will be discussed. Large enhancements at RT is 102 !,C/cm2, which is considerably higher than previously in higher order nonlinear optical effects such as nonlinear absorption reported for BFO. Moreover, decreasing the temperature down to 90 and nonlinear refraction in Bi-based ferroics will also be presented. K allowed us to obtain GFP such as Pc of 146 !,C/cm2 and a saturation polarization (P,) of 158 !,C/cm2 with a coercive field of 9:15 AM H1.3 120 kV/cm at 20 V maximum applied voltage. These values are the Large Second Harmonic Generation (SHG) in GaFe03 pulsed highest in ferroelectric materials ever-measured so far. We obtained laser deposited thin films on YSZ buffered silicon. 2 good reproducibility of these values of polarization when changing the Darshan C. Kundaliya', S. B. Ogale', S. E. Lofiand , Keith measured capacitor. The hysteresis loops at 90 K have a saturated McDonald2, Ernst Knoesel2 , S. R. Shinde' and T. Venkatesan'; rectangular shape and do not show evidence of large leakage current lCenter for Superconductivity Research, Department of Physics, when measured at 1 kHz frequency. The memorized polarization University of Maryland, College Park, Maryland; 2Department of during a standard retention measurement of our BFO thin films has Chemistry and Physics, Rowan University, Glassboro, New Jersey. been well maintained. In addition, the BFO thin films have shown good multiferroic properties. The magnetization-magnetic field Gallium Iron Oxide (GaFe03) is a compound which exhibits (M - H) loops of the films measured at RT show a well-saturated ferromagnetic and piezoelectric properties simultaneously. This kind weak ferromagnetic hysteresis characteristic with saturation 3 of non-centrosymmetric polar ferromagnet also produces giant magnetization M, of 40 emu/cm for a maximum magnetic field of 10 magneto-optical kerr effect (MOKE) as reported recently in a single kOe. The piezoelectric hysteresis loop of the films measured by AFM crystal [1]. We report the epitaxial growth of GaFe03 thin films on also show a piezoelectricity of 66 pm/V, which is comparable to the silicon with a Y-Zr02 (YSZ) buffer layer and without chemical value obtained from epitaxial BFO thin films on STO single crystal removal of the surface oxygen on silicon. The X-ray diffraction pattern substrate. shows c-axis orientation of YSZ and b-axis orientation of GaFe03 on Si (100) substrate. Ferromagnetic transition temperature (Te 220 K) 10:30 AM H1.6 is in good agreement with the bulk data. We performed the analyzer Systematic investigation of multiferroic properties