Participants

Gopalan Srinivasan [Co-PI]
Uladzimir Laletsin [Postdoc]
Pitamber Mahanadia [Postdoc]
Vikas Mathe [Postdoc]
Roman Petrov [Postdoc]
Vincy Gheevarughese [Grad student]
Christopher DeVreugd [Grad student]
Maksym Popov [Grad student]
David Elliott [Undergrad]
Saurabh Pandey [REU]
Nimit Jain [High school senior]
Harini Srinivasan [High school senior]
Sneha Inguva [High School senior]
Rahul Pandey [High school student]
Pratyusha Yalamanchi [High school student]
Sourya Naraharisetti [High school student]
Ananya Mukundan [High school student]

Collaboration

Moscow Institute of Radio Engineering, Russia: Professor Yuri Fetisov
St. Petersburg Electrotechnical University, Russia: Professor Boris Kalinikos
Novgorod State University, Russia: Professors Vladimir Petrov and Dmitry Filippov
University of Kiev, Ukraine: Prof. Igor Zavislyak
Moscow Power Engineering Institute: Professor Balbashov
International Academy, Bloomfield, Michigan: 3 high school seniors spent the summer of 2006 and performed research

Activities

The Oakland University group is involved in the modeling and magnetoelectric (ME) characterization of ferromagnetic-ferroelectric nanostructures and analysis of magnetoelectric interactions. The sample response to ac electromagnetic fields is investigated over a wide frequency range, from 1 mHz to 10 GHz and involves studies on the following ME phenomena.

  1. Low frequency ME effects (10 Hz-10 kHz).
  2. ME dispersion and Maxwell-Wagner relaxation (1 mH-100 Hz).
  3. Resonance enhancement of ME coupling at electromechanical resonance (EMR) (100 kHz – 2 GHz).
  4. Microwave ME interactions through ferromagnetic resonance (1-10 GHz).
  5. ME coupling at magneto-acoustic resonance (1-10 GHz).

Major Findings

Significant accomplishments include (i) theory of low-frequency ME interactions in ferrite-PZT nanobilayers, pillars and wires; (ii) effects of voids/porosity on ME interactions, (iii) theory of Maxwell-Wagner relaxation, (iv) microwave ME interactions in ferrite-PZT nanobilayers, and (v) measurement techniques for non-linear and inverse ME effects.

1. Theory of Magnetoelectric Effects in Ferrite-Piezoelectric Nanocomposites [Phys. Rev. B75, 224407 (2007)].
A model was developed for low-frequency ME effects in nanobilayers, nanopillars and nanowires of nickel ferrite (NFO) and lead zirconate titanate (PZT) on MgO substrates or templates. The clamping effects of the substrate for the bilayer and pillars and of the template for the wires were considered in determining the ME voltage coefficient. The ME interactions were found to be the strongest for field orientations corresponding to minimum demagnetizing fields (Fig. 1).

Fig.1.  Diagram showing a nickel ferrite (NFO)- lead zieconate titanate (PZT) nanobilayer in the (1,2) plane on MgO substrate. It is assumed that PZT is poled with an electric field E1 along 1, the bias magnetic field H1 and ac magnetic field δH1 are along axis-1 and the ac electric field δE1 is measured along direction-1. Estimated PZT volume fraction dependence of in-plane longitudinal ME voltage coefficient is shown for a series of volume fraction vs for MgO.

2. Magnetoelectric Effects in Porous Ferromagnetic-Piezoelectric Bulk Composites: Experiment and Theory [Phys. Rev. B 75, 174422 (2007)]
Porosity in bulk composites is similar to voids in nanopillars. The dependence of magnetoelectric (ME) parameters on porosity has been investigated in ferrite-piezoelectric bulk composites. A model that considers the influence of porosity on ME interactions has been developed. The calculated ME coefficients are in very good agreement with the data.

3. Dispersion Characteristics for Low-Frequency Magnetoelectric Coefficients in Bulk Ferrite – Piezoelectric Composites [Solid State Commun. 142, 515 (2007)]
A theory for the low-frequency Maxwell-Wagner relaxation in ME coefficients is discussed for bulk composites of nickel or cobalt ferrite and lead zirconate titanate (PZT). ME coefficients versus frequency spectra show two types of relaxation, over 0.1- 100 μHz and 1-1000 Hz. The relaxation frequencies and the magnitude of the ME coefficients are dependent on the electrical and composite parameters and volume fraction for the two phases. The ME coefficient is in the range 10-1 – 104 mV/cm Oe, higher in cobalt ferrite-PZT than for nickel ferrite-PZT, and is strongly dependent on PZT volume fraction v. Estimates of ME coefficients provided are useful for engineering composites with maximum ME effects for specific frequency bands.

4. Theory of electric field induced magnetic excitations in ferrite-piezoelectric nanobilayers [Solid State Commun. 144, 50 (2007)]
A theory for magnetic excitations in a yttrium iron garnet (YIG)-PZT nanobilayer due to microwave electric field and magneto-electric (ME) interactions is discussed. The magnetic response is described by ME susceptibility and a technique has been proposed for its determination. The electric field excites elastic modes in PZT that would result in magnetoelastic modes in YIG. The model predicts maximum ME susceptibility when the microwave field is at the coincidence of electro-mechanical and magnetic resonance. The theory is of importance for new devices such as magnetoelectric spin-acoustic wave generators and power limiters.

5. Effects of exchange-interactions on magneto-acoustic resonance in layered nanocomposites of yttrium iron garnet and lead zirconate titanate [Journal of Materials Research 22, 2174 (2007)]
The effect of magnetic exchange interactions on ME coupling at magneto-acoustic resonance (MAR), i.e., at the coincidence of electromechanical resonance in the piezoelectric phase and ferromagnetic resonance in a tangentially magnetized ferrite. The magnetic exchange is predicted to enhance the coupling at MAR and produce a secondary peak due to the excitation of magnetoacoustic modes.

6. Low-Frequency Non-Linear Magnetoelectric Effects in a Ferrite-Piezoelectric Multilayer [Appl. Phys. Lett. 89, 142510 (2006)]
A technique for the measurements of non-linear magnetoelectric (ME) effects has been developed.

7. Inverse Magneto-electric effects [J. Mater. Res. 22, 2074 (2007)]
The first measurements of inverse magnetoelectric effects (ME) in a lead zirconate titanate (PZT)-Ni-PZT trilayers are reported. Traditional ME measurements involve electrical response of a composite subjected to an ac magnetic field. In the case of inverse ME effect, one measures variation in the magnetic induction due to an external ac electric field applied to PZT. The technique is useful for ME characterization of nanocomposites.

8. Resonance magnetoelectric interactions due to bending modes in a Ni-PZT bilayer [Appl. Phys. Lett. 92, 102511 (2008)]
Resonance magnetoelectric effects due to bending oscillations were investigated in bilayers of Ni and PZT. The phenomenon is of importance in nanocomposites. For nominal sample dimensions, such oscillations occur at a few kHz that are much smaller than radial or thickness modes and result in ME voltage coefficients of 1 V/cm Oe for tangential magnetization. The mode frequencies can be controlled with proper choice for thicknesses of Ni and PZT layers and are potentially useful for realizing low-loss ME sensor networks for ac fields as low as 10 μOe.

9. ME coupling in hexaferrite-PZT bilayers [Appl. Phys. Lett. 92, 122505 (2008)]
Hexaferrites have very high uniaxial or planar anisotropy field and are ideal for use as high magnetic field nanosensors. Our studies on single crystal ferrite-PZT bilayers show strong ME coupling for fields as high as 2 T.

10. A comprehensive review on “Multiferroic magnetoelectric composites: Historical perspective, status and future directions.” [J. Appl. Phys. 103, 031101 (2008)].

Outreach Activities

Three high school seniors (from the International Academy, Bloomfield, Michigan) spent the summer of 2006 on research projects on (i) Magnetoelectric composites for miniature antennas and (ii) Magnetoelectric field sensors. The students submitted two reports for the Siemens - 2006 competitions. One of the two teams was selected as the finalist for the Mid-west region and presented their project at the University of Notre Dame.

Siemens Competition ( http://www.siemensfoundation.org/competition/ ).

The 2006 team (Harini and Nimit) was a Mid-West regional finalist.
(http://www.siemens-foundation.org/competition/2006/notredame.htm)

Nimit Jain & Harini Srinivasan, International Academy, Bloomfield Hills, Michigan. Ferrite-Ferroelectric Composites for Miniature Antennas: Nimit Jain and Harini Srinivasan’s physics project researched new composite materials which could be used for highly miniaturized antennas for communication networks, radar systems, mobile phones and remotely controlled systems. Their research has the potential to dramatically impact radar and communications systems for a variety of sectors including consumer electronics and national defense.

Recent Publications

  1. Ce-Wen Nan, M. I. Bichurin, S. Dong, D. Viehland, and G. Srinivasan, “Multiferroic magnetoelectric composites: Historical perspective, status and future directions,” J. Appl. Phys. 103, 031101 (2008). [View article]
  2. M. Vopsaroiu, M. Stewart, T. Hegarty, A. Muniz-Piniella, N. McCartney, M. Cain, and G. Srinivasan, “Experimental determination of the magnetoelectric coupling coefficient via piezoelectric measurements,” Meas. Sci. Technol. 19, 045106 (2008). [View article]
  3. D.V. Chashin, Y.K. Fetisov, and K.E. Kamentsev, and G. Srinivasan, “Resonance magnetoelectric interactions due to bending modes in a Ni-PZT bilayer,” Appl. Phys. Lett. 92, 102511 (2008). [View article]
  4. V. L. Mathe, G. Srinivasan, and A. M. Balbashov, “Magnetoelectric effects in bilayers of lead zirconate titanate and single crystal hexaferrites,” Appl. Phys. Lett. 92, 122505 (2008). [View article]
  5. V. M. Petrov, G. Srinivasan, M. I. Bichurin, and A. Gupta, "Theory of magnetoelectric effects in ferrite piezoelectric nanocomposites," Phys. Rev. B 75, 224407 (2007). [View article]
  6. V. M. Petrov, G. Srinivasan, U. Laletsin, M. I. Bichurin, D. S. Tuskov, and N. Paddubnaya, "Magnetoelectric effects in porous ferromagnetic-piezoelectric bulk composites: Experiment and theory," Phys. Rev. B 75, 174422 (2007). [View article]
  7. O. V. Ryabkov, S. V. Averkin, and M. I. Bichurin, "Effects of exchange interactions on magnetoacoustic resonance in layered nanocomposites of yttrium iron garnet and lead zirconate titanate," J. Mater. Res. 22 (8) 2174-2178 (2007). [View article]
  8. Y. K. Fetisov, V. M. Petrov, G. Srinivasan, "Inverse magnetoelectric effects in a ferromagnetic–piezoelectric layered structure," J. Mater. Res. 22 (8) 2074-2080 (2007). [View article]
  9. V.M. Petrov, M.I. Bichurin, G. Srinivasan, Junyi Zhai and D. Viehland, "Dispersion characteristics for low-frequency magnetoelectric coefficients in bulk ferrite-piezoelectric composites,"  Solid State Commun. 142 515 (2007). [View article]
  10. V. Petrov, G. Srinivasan, O. V. Ryabkov, S. V. Averkin and M. I. Bichurin, "Microwave magnetoelectric interactions in ferrite–piezoelectric nanobilayers: Theory of electric field induced magnetic excitations," Solid State Communications, 144, 50 2007. [View article]
  11. M. I. Bichurin, D. Viehland and G. Srinivasan, "Magnetoelectric interactions in ferromagnetic-piezoelectric layered structures: Phenomena and devices," J. of Electroceram. In Press, Available online 28 February 2007. [View article]
  12. K. E. Kamentsev, Y. K. Fetisov, and G. Srinivasan, "Low-frequency nonlinear magnetoelectric effects in a ferrite-piezoelectric multilayer," Appl. Phys. Lett. 89, 142510 (2006). [View article]