Magnetoelectric Multiferroic Thin Films and Multilayers: Magnetoelectric Hetrostructures, Noise Reduction, and Techniques for Enhanced Sensitivity
Program Organizers: Shashank Priya, Virginia Tech; Dwight Viehland, Virginia Polytechnic Institute and State University; Ram Katiyar, University of Puerto Rico; Koduri Ramam, Universidad de Concepción, Departamento de Ingeniería de Materiales (DIMAT); Gopalan Srinivasan, Oakland University; Nian Sun, Northeastern University

Tuesday 2:00 PM
October 9, 2012
Room: Room 324
Location: David L. Lawrence Convention Ctr

Session Chair: Nian Sun, Northeastern University

2:00 PM
Enhancement in Magnetic Field Sensitivity and Reduction in Equivalent Magnetic Noise by Magnetoelectric Laminate Arrays: Menghui Li¹; Junqi Gao¹; Yaojin Wang¹; Jiefang Li¹; Dwight Viehland¹; ¹Virginia Tech
     The magnetoelectric (ME) effects in Metglas/piezo-fiber laminates have been investigated due to potential applications in magnetic sensors. ME laminate sensor arrays have been predicted to effectively increase the signal-to-noise ratio. In such arrays, the effect of mutual inductance of the Metglas is quite significant.In this work, finite element simulation using MAXWELL 13.0 was performed for the flux density in Metglas foils. Separation distances of >40 mm were found to make the effect of mutual inductance small for a pair of ME laminate sensors. The modeled and measured equivalent magnetic noise decreased by a factor of √N and the magnetic field sensitivity increased with increasing for a ME sensor unit of N numbers of ME laminates. For Metglas/Pb(Mg1/3,Nb2/3)O3-PbTiO3 laminates, the equivalent magnetic noise decreased and the magnetic field sensitivity increased by a factor of 2.1 and 2.3 respectively, for N=4 relative to N=1.

2:20 PM
Size-Dependent Converse Magnetoelectric Switching in Multiferroic Heterostructures: Phase-Field Modeling and Device Applications: Jiamian Hu¹; Zheng Li¹; Long-Qing Chen²; Ce-Wen Nan¹; ¹Tsinghua University; ²Pennsylvania State University
    We study the size-dependent converse magnetoelectric switching of magnetization in layered multiferroic heterostructures using phase-field simulations. We obtain electric-voltage induced changes in both the macroscopic magnetization and magnetic domain structures. Based on the simulations, we proposed a new device concept for a simple voltage-controlled Magnetoresistive Random Access Memory (MRAM). The proposed nanoscale memory device can achieve ultrahigh storage capacity, ultralow power dissipation, and room-temperature high-speed operation simultaneously, thus offering a potentially significant improvement over existing MRAM technologies or existing device concepts.

3:00 PM Break

3:20 PM  Cancelled
Substrate Influence on Properties of Pulsed Laser Deposited BiFeO3 Epitaxial Films: Rajesh Katiyar¹; Tanaji Gujar¹; Ram Katiyar¹; ¹University of Purto Rico
    Among many ferroelectric photovoltaic materials, bismuth ferrite BiFeO3 (BFO) has a few interesting and unique properties. BFO, a multiferroic material at room temperature with direct band gap of nearly 2.74 eV and a very large remnant ferroelectric polarization, offers a unique opportunity for photovoltaic applications. It has appreciable photoconductivity in the visible light as well as it has high absorption coefficient. Recently, switchable-diode effect and a visible-light photovoltaic effect has been observed in BFO. The epitaxial BFO films deposited by pulsed laser deposition (PLD) on SrTiO3/SiO2/Si, Pt/TiO2/SiO2/Si, Pt/Dy2O3/Si and Au/Dy2O3/Si were studied using Raman spectroscopy, x-ray diffraction, atomic force microscopy, piezoelectric force microscopy, vibrating sample magnetometry, and electric characterization. The phase pure BFO films were confirmed by Raman spectroscopy and x-ray diffraction investigations. The surface morphological studies reveal that the grown films are very smooth and with uniform grain distribution. Additionally, the ferroelectric performance of BFO was observed by PFM.

3:40 PM
X-Ray Based Characterization of Magnetoelectric Multilayers: Jinling Zhou¹; Srinivas Polisetty¹; Evan Wolfe¹; Charles Frye¹; Disheng Chen¹; Mikel Holcomb¹; Catherine Jenkins¹; Andreas Scholl¹; Ying-Hao Chu¹; ¹West Virginia University
    Magnetoelectric (ME) coupling---the electrical control of magnetic properties or vice versa---has promising applications in computer memory and logic, magnetic sensing and energy scavenging. Understanding the coupling mechanisms in a variety of magnetoelectric material systems will allow us to design better magnetoelectric systems. Our group studies the interfacial magnetoelectric coupling in La_0.7Sr_0.3MnO₃ (LSMO) and PbZr_0.2Ti_0.8O₃ (PZT) multilayer heterostructures. Through x-ray based photoemission electron microscopy imagining and x-ray absorption spectroscopy at a variety of LSMO and PZT thicknesses, ME coupling was confirmed at the interface and the depth dependence of Mn valences are extensively explored. Based on our discovery, the strength of magnetoelectric coupling in multilayer systems could be controlled through thickness engineering.

4:20 PM
Structural, Magnetic and Electrical Properties of Epitaxial ultrathin PbZr0.52Ti0.48O3 Films Prepared on La0.67Sr0.33MnO3/(LaAlO3)0.3(Sr2AlTaO6)0.7 Substrates: Danilo Barrionuevo Diestra¹; Nora Ortega¹; Ashok Kumar¹; Ram Katiyar¹; ¹University of Puerto Rico Rio Piedras
    A way to exploit the ferroelectric (FE) properties of PbZr0.52Ti0.48O3 (PZT) ultrathin film materials is to design tunnel junctions integrating FE film as the tunnel barrier. We have studied the thickness effect of PZT thin films with thickness from 100 to 3 nm on La0.67Sr0.33MnO3(LSMO)/(LaAlO3)0.3(Sr2AlTaO6)0.7 (001) substrates by pulsed laser deposition technique. The AFM studies show that the surface roughness on a 3 x 3 µm2 area of 100 and 3 nm thick films were 1.89 and 0.24 nm respectively. Well saturated FE loops were observed for PZT films with 100, 50 and 25 nm thickness with a remanent polarization of 35, 33 and 31 µC/cm2 respectively. The ferroelectricity in 7, 5 and 3 nm PZT ultrathin films was confirmed using PFM. An enhancement in FE properties was observed with reduction in deposition rate. The effect of PZT film thickness on Curie temperature and LSMO magnetic properties will be discussed.