Conventional CMOS based logic and magnetic based data storage devices require the shuttling of electrons for data processing and storage. As these devices are scaled to increasingly smaller dimensions in the pursuit of speed and storage density, significant energy dissipation in the form of heat has become a center stage issue for the microelectronics industry. By taking advantage of the strong correlations between ferroic orders in multiferroics, specifically the coupling between ferroelectric and magnetic orders (magnetoelectricity), new device functionalities with ultra-low energy consumption can be envisioned. In this article, we review the advances and highlight challenges toward this goal with a particular focus on the room temperature magnetoelectric multiferroic, BiFeO3, exchange coupled to a ferromagnet. We summarize our understanding of the nature of exchange coupling and the mechanisms of the voltage control of ferromagnetism observed in these heterostructures.
J.T.H. acknowledges that this research was made with government support awarded by DOD, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a. We thank C. M. Brooks and H. Nair for their comments on this manuscript. The authors recognize that this material is based upon work supported by the National Science Foundation (Nanosystems Engineering Research Center for Translational Applications of Nanoscale Multiferroic Systems) under Grant Number EEC-1160504 and the D.O.D.-A.R.O. M.U.R.I supported by the Army Research Office through Agreement Number W911NF-08-2-0032. R.R. acknowledges the support of the Director, Office of Basic Energy Sciences, Materials Science Division of the US Department of Energy under Contract Number DE-AC02-05CH11231, the NSF MRSEC (DMR-00-80008), the Center for Energy Efficient Electronics Science (NSF Grant Number 0939514), the Western Institute of Nanoelectronics program, the STARnet FAME, as well as significant intellectual and financial support from scientists and engineers at Intel (e.g. Dmitri Nikonov). Finally, we would like to express our appreciation to all of the collaborators and coauthors for the work presented herein, specifically K. Ashraf, Y.-H. Chu, R. Dynes, M. Gajek, Q. He, L. W. Martin, S. Salahuddin, M. Trassin, S. Wu, and P. Yu. Additionally, we would like to express our gratitude to M. Viret and J. Wang for the permissions to reuse their works.
A. BiFeO3: A room temperature single-phase magnetoelectric multiferroic
II. EXCHANGE COUPLING IN FERROMAGNET/BiFeO3 HETEROSTRUCTURES
A. Exchange coupling with transition metal ferromagnets (TMFs)
1. Single domain bulk crystals
2. Multidomain thin films: Effect of domain walls
3. Multidomain thin films: Effect of domain structure
B. Exchange coupling with oxide ferromagnets
III. ELECTRIC FIELD CONTROL OF MAGNETISM
A. Electric field control of antiferromagnetism
B. Electric field control of exchange bias
C. Electric field control of magnetization direction without exchange bias
D. Electric field control with single domain BiFeO3 crystals
E. Electric field control with multidomain BiFeO3 thin films
IV. WHAT ARE THE ISSUES?: CHALLENGES AND FUTURE DIRECTIONS
A. Magnetoelectric switching with an out-of-plane electric field
B. Integration with silicon
C. Electrically controlled magnetic memory or logic element
D. Fatigue and reliability
Data & Media loading...
Article metrics loading...
Full text loading...