Participants

Arunava Gupta [Co-PI]
Haizhong Guo [Postdoc] (2006)
Prahallad Paddhan [Postdoc] (2007)
Gunwoo Kim [Graduate Student]
John Andrew Sherrill [Undergraduate REU]

Collaboration

Oak Ridge National Laboratory: Dr. M. Varela & Dr. S. Pennycook - Scanning Transmission Electron Microscopy/EELS
University of Houston: Dr. Milko Iliev - Polarized Raman Spectroscopy
Oregon State University: Prof. Mas Subramanian - Bulk Double-Perovskite Materials
Alabama A&M University: Dr. S. Budak, Dr. C. Muntele, Prof. Daryush Ila - Rutherford Backscattering Spectroscopy

Activities

The UA group's focus is on the synthesis and characterization of novel double perovskite-based multifunctional oxide thin films and heterostructures using the pulsed laser deposition technique. The intent is for a better understanding of the growth, structure-property relationship, and physics of these complex oxides, and also for tuning their properties. The ultimate goal is to achieve robust room-temperature magnetoelectric properties that will be useful for practical applications.

Arun Gupta has given following invited presentations on NIRT-related work:

Major Findings

Epitaxial thin films of La2NiMnO6 and Bi2NiMnO6 have been synthesized for the first time  A related ferromagnetic semiconductor, La2CoMnO6, has also been grown epitaxially. High quality epitaxial films of these double perovskites are grown on lattice-matched substrates such as SrTiO3, NdGaO3 and LaAlO3 using pulsed laser deposition (PLD). These films have been structurally characterized using a variety of techniques, including Raman spectroscopy and high-resolution electron microscopy. The temperature-dependent magnetic properties have also been investigated. While La2NiMnO6 exhibits normal ferromagnetic behavior below the Curie temperature of 275 K, a spin-glass type behavior is observed in the case of La2CoMnO6.

During the past year, we have studied in detail the growth behavior of La2NiMnO6 and La2CoMnO6 as a function of oxygen background pressure. We have determined that the ordered double perovskite phase is obtained at relatively high (> 200 mTorr) oxygen pressures, with defect phases being stabilized at lower pressures. We have also grown films of Bi2NiMnO6 and confirmed that they exhibit multiferroic behavior. Furthermore, both La2NiMnO6 and Bi2NiMnO6 exhibit magnetodielectric effect – i.e., a change in dielectric constant with application of a magnetic field. However, the effect is limited to low temperatures (~ 150 K) in these materials. We have expanded to growing heterostructures of the double perovskites by artificially layering these multifunctional materials with other related oxides in order to tailor their properties. In addition to studying the intrinsic multiferroic properties of the double perovskite compounds and their heterostructures, we have also initiated work on ferromagnetic-ferroelectric composite films to investigate the magnetoelectric coupling.

Recent Publications

  1. P. Padhan, P. LeClair, A. Gupta, and G. Srinivasan, “Magnetodielectric Response in Epitaxial Thin Films of Multiferroic Bi2NiMnO6,” Appl. Phys. Lett., submitted.
  2. M. N. Iliev, P. Padhan, and A. Gupta, “Temperature-dependent Raman Study of Multiferroic Bi2NiMnO6 Thin Films,”  Phys. Rev. B, in review.
  3. P. Padhan, H. Z. Guo, P. LeClair, and A. Gupta, "Dielectric relaxation and magnetodielectric response in epitaxial thin films of La2NiMnO6,” Appl. Phys. Lett. 92, 022909 (2008). [View article]
  4. H. Z. Guo, J. Burgess, E. Ada, S. Street, A. Gupta, M. N. Iliev, A. J. Kellock, M. Varela, and S. Pennycook, “Influence of defects on the structural and magnetic properties of multifunctional La2NiMnO6 thin film,” Phys. Rev. B 77, 174423 (2008). [View article]
  5. J. Burgess, H. Z. Guo, A. Gupta, and S. Street, “Raman Spectroscopy of La2NiMnO6 films on SrTiO3(100) and LaAlO3(100) Substrates: Observation of Epitaxial Strain,” Vibrational Spect., in print (2007). [View article]
  6. H. Z. Guo, A. Gupta, J. Zhang, M. Varela, S. J. Pennycook, “Effect of Oxygen Concentration on the Magnetic Properties of La2CoMnO6 Thin Films,” Appl. Phys. Lett. 91, 202509 (2007). [View article]
  7. S. Budak, C. Muntele, I. Muntele, H. Guo, A. Gupta, and D. Ila, “RBS Study of Epitaxially Grown Thin Films of the Double Perovskite La2NiMnO6”, Nucl. Inst. and Meth. B 261, 686 (2007). [View article]
  8. M. N. Iliev, M. V. Abrashev, A. P. Litvinchuk, V. G. Hadjiev, H. Guo, and A. Gupta, “Raman Spectroscopy of Ordered Double Perovskite La2CoMnO6 Thin Films”, Phys. Rev. B 75, 104118 (2007). [View article]
  9. V. Petrov, G. Srinivasan, M. I. Bichurin, and A. Gupta, “Theory of Magnetoelectric Effect in Ferrite Piezoelectric Nanocomposites”, Phys. Rev. B 75, 224407 (2007). [View article]
  10. M. Iliev, H. Guo and A. Gupta, “Raman Spectroscopy Evidence of Strong Spin-Phonon Coupling in Epitaxial Thin Films of the Double Perovskite La2NiMnO6”, Appl. Phys. Lett. 90, 151914 (2007). [View article]
  11. H. Z. Guo, A. Gupta, T. G. Calvarese, and M. A. Subramanian, “Structural and Magnetic Properties of Epitaxial Thin Films of the Ordered Double Perovskite La2CoMnO6,” Appl. Phys. Lett. 89, 262503 (2006). [View article]