I just read Ising's interesting introduction of Multiferrotics several days ago. Today there is a coloquium about it by professor Jeroen van den Brink of University of Leiden. So I post the introduction of his speech here for those who are interested.
================================================= Title : Novel routes to Multiferroic Speaker : Jeroen van den Brink, Universiteit Leiden
Abstract : As this new century unfolds the study of materials possessing coupled magnetic and ferroelectric order - multiferroics - is revitalized, after pioneering work in the 1950s-1960s [1,2]. New classes of materials were found to be ferroelectric and exhibiting an exceptionally strong sensitivity to applied magnetic fields. These multiferroics show many dramatic effects, such as a giant magneto-capacitance, magnetically induced electric polarization flops and a rotation of electric polarization in a periodically varying magnetic field [3-5]. These effects are not only interesting from a fundamental point of view but can also be directly relevant for sensor, transducer and memory device applications [2]. This motivated Science Magazine a few months ago to identify the field of multiferroics as an Area to Watch [6]. In the colloquium I will discuss new theoretical possibilities to obtain multiferroic couplings in systems that exhibit combinations of charge and spin order [6-10].
[1] N. Spaldin and M. Fiebig, Science 309, 391 (2005). [2] W. Eerenstein, N. Mathur and J. F. Scott, Nature 442, 759 (2006). [3] T. Kimura, et al., Nature 426, 55 (2003). [4] T. Goto, et al., Phys. Rev. Lett. 92, 257201 (2004). [5] N. Hur, et al., Nature 429, 392 (2004). [6] Science, 318, 21 (2007). [7] D. Efremov, J. van den Brink and D. Khomskii, Nature Materials 3, 853 (2004). [8] J. Betouras G. Giovannetti and J. van den Brink, Phys. Rev. Lett. 98, 257601 (2007). [9] G. Giovannetti and J. van den Brink, preprint cond-mat/0802.0653 (2008). [10] J. van den Brink and D. Khomskii, preprint cond-mat/0803.2964 (2008).