ABSTRACT
Contents 6.1 Introduction................................................................................................. 166 6.2 Direct ME Eect in Bulk Multiferroic Composites ............................... 168
6.2.1 Characterizing the Direct ME Eect .......................................... 168 6.2.2 Historical Background of Direct ME Eect .............................. 169 6.2.3 Current Status of Direct ME Eect Study .................................. 171
6.2.3.1 Self-Biased Direct ME Eect ........................................ 171 6.2.3.2 Nonlinear Direct ME Eect ......................................... 173
6.3 Converse ME Eect .................................................................................... 175 6.3.1 Characterizing the Converse ME Eect ..................................... 175 6.3.2 Historical Background of Converse ME Eect ......................... 176 6.3.3 Current Status of Converse ME Eect ........................................ 178
6.3.3.1 Dynamics of Converse ME Eect ............................... 178 6.3.3.2 Converse ME Eect at the Mesoscale ......................... 179
6.4 Conclusion and Outlook ............................................................................ 181 Acknowledgments ................................................................................................. 181 References ............................................................................................................... 182
6.1 Introduction In bulk magnetoelectric (ME) composites, the linear ME eect is a product of piezomagnetic and piezoelectric eects of the constituting phases (while the nonlinear ME eect involves nonlinear magnetostriction and/or electrostriction), and can be expressed as [1]
= ×
= ×
Direct ME effect electric mechanical
mechanical magnetic
Converse ME effect magnetic mechanical
mechanical electric
(6.1)
In this case, magnetic eld (H)–induced charge/voltage output (direct ME eect), or electric eld (E)–controlled magnetism (converse ME eect) is achieved via strain transfer across the interface. e cross coupling leads to new functionalities that are not available in either of the constituting phases and opens tantalizing possibilities for various technologies. For example, the direct ME eect converts the magnetic eld into electric signals at room temperature without any other power source. It is very sensitive and can potentially revolutionize the current superconducting quantum interference devices (SQUID)–based technology, which is bulky, expensive, and only operates at low temperatures [2]. e converse ME eect enables the modulation of magnetization by electric elds rather than by power-consuming electric currents, and can be used to design next generation nonvolatile memories and low-power electric-eld tunable microwave devices [3]. A detailed discussion on various applications of bulk ME composites is presented in Chapter 8 of this book.
