# Presentation: 950211

## Giant Magnetoelectric Effects in Ferromagnetic-Ferroelectric HeterostructuresG. Srinivasan, Oakland University, DMR-0302254  

**The research is directed toward the measurements and theoretical understanding of   magnetoelectric (ME) interactions at 10 Hz – 10 GHz in layered structures consisting of ferrites and lead zirconate titanate (PZT).  The ME coupling is mediated by mechanical stress. Our activities during the past year involved: (i) Studies on ME interactions at ferromagnetic resonance FMR for ferrites that revealed a strong coupling (Fig.1); (ii) theory of ME effects at magneto-acoustic resonance (MAR) that predicted a giant ME coefficient at the coincidence of FMR and electromechanical resonance (Fig.2). **

**Giant Magnetoelectric Effects in Ferromagnetic-Ferroelectric Heterostructures****G. Srinivasan, Oakland University, DMR-0302254**** **

**Phys. Rev. B 70, 064416 (2004)**
**Phys. Rev. B 72, 060408(R) (2005)**
**Appl. Phys. Lett. 87, 103502 (2005)**

**Fig.1:  Electric field effects at FMR in a bilayer of yttrium iron garnet and PZT.**

**                ****Frequency (GHz)**

**ME Voltage Coeff. (V/cm Oe)**

**Fig.2: ME coupling at MAR in YIG/PZT**

**Notes:**
Figure 1 shows experimental evidence for the influence of electric field on ferromagnetic resonance in YIG. Microwave signal processing devices such as filters are tuned by a variable magnetic field which requires very high power and the tuning is slow.  When YIG is replaced by a YIG/PZT bilayer, the device can be tuned with an easy to produce electric field.
Figure 2 shows theoretical predictions of very high ME coupling at magneto-acoustic resonance in YIG-PZT and the potential for nano microwave power sensors and transducers.

## Giant Magnetoelectric Effects in Ferromagnetic-Ferroelectric HeterostucturesG. Srinivasan, Oakland University, DMR-0302254  

**Education and Research training**: Four high school junior/senior, 3 undergraduates, two graduate students and two research associates were involved in the research. Their training included materials synthesis and characterization, data acquisition and analysis and theory of materials.
**Publications and Presentations**
- Journal Publications:20
- Undergraduate coauthored publications: 12
- Conference Presentations: 22

_**Smart Signal processors:**_
**The ME composites are potential candidates for magnetoelectric memory devices, smart sensors, electrically controlled magnetic devices, and magnetically controlled piezoelectric devices. Recently we demonstrated several microwave signal processing devices based on ME composites that can be tuned with an electric field.** **Joint projects are in progress with Delphi Corporation on such devices for radars in cars.**** **
_**Research Experience for High School Students:**_** Four high school interns (supported by NSF funds) spent the summer of 2004 and 2005 in our group.  They successfully completed their projects on ME sensors.   Reports were  submitted for International Baccalaureate (IB) program, Intel Science Talent Search, and Siemens-Westinghouse competitions (SWC).  The 2005 team from the International Academy, Bloomfield Hills, MI (Andrew King and Sneha Inguva) submitted a report on “Magnetoelectric composites for magnetic field sensors,” based on their summer research and have advanced to the semi-finals of the  SWC.****  **

**Giant Magnetoelectric Effects in Ferromagnetic-Ferroelectric Heterostuctures****G. Srinivasan, Oakland University, DMR-0302254**** **

**Notes:**
Electric field tunable microwave devices can be integrated with semiconductor technology, and will lead to miniature, frequency agile signal processors that will have applications in radars and communication systems of importance for consumer and defense related electronics.