Multiferroics are of interest for memory and logic device applications, as the coupling between ferroelectric and magnetic properties enables the dynamic interaction between these order parameters. Here, we report an approach to control and switch local ferromagnetism with an electric field using multiferroics. We use two types of electromagnetic coupling phenomenon that are manifested in heterostructures consisting of a ferromagnet in intimate contact with the multiferroic BiFeO(3). The first is an internal, magnetoelectric coupling between antiferromagnetism and ferroelectricity in the BiFeO(3) film that leads to electric-field control of the antiferromagnetic order. The second is based on exchange interactions at the interface between a ferromagnet (Co(0.9)Fe(0.1)) and the antiferromagnet. We have discovered a one-to-one mapping of the ferroelectric and ferromagnetic domains, mediated by the colinear coupling between the magnetization in the ferromagnet and the projection of the antiferromagnetic order in the multiferroic. Our preliminary experiments reveal the possibility to locally control ferromagnetism with an electric field.

Abstract. During the previous cloning of the fibrillin gene (FBN1), we isolated a partial eDNA coding for a fibrillin-like peptide and mapped the corresponding gene (FBN2) to human chromosome 5. (Lee, B., M. Godfrey, E. Vitale, H. Hori, M. G. Mattei, M. Sarfarazi, P. Tsipouras, E Ramirez, and D. W. Hollister. 1991. Nature [Lond.]. 352:330-334). The study left, however, unresolved whether or not the FBN2 gene product is an extracellular component structurally related to fibrillin. Work presented in this report clarifies this important point. Determination of the entire primary structure of the FBN2 gene product demonstrated that this polypeptide is highly homologous to fibrillin. Immunoelectron microscopy localized both fibrillin proteins to elastin-associated extracellular mierofibrils. Finally, immunohistochemistry revealed that the fibrillins co-distribute in elastic and nonelastic connective tissues of the developing embryo, with preferential accumulation of the FBN2 gene product in elastic fiber-rich matrices. These results support the original hypothesis that the fibriUins may have distinct but related functions in the formation and maintenance of extracellular microfibrils. Accordingly, we propose to classify the FBN1 and FBN2 gene products as a new family of extracellular proteins and to name its members fibrillin-1 and fibrillin-2, respectively.

Abstract. Extracellular microfibrils, alone or in association with elastin, confer critical biomechanical properties on a variety of connective tissues. Little is known about the composition of the microfibrils or the factors responsible for their spatial organization into tissue-specific macroaggregates. Recent work has revealed the existence of two structurally related microfibrillar components, termed fibrillin-1 and fibrillin-2. The functional relationships between these glycoproteins and between them and other components of the microfibrils and elastic fibers are obscure. As a first step toward elucidating these important points, we compared the expression pattern of the fibrillin genes during mammalian embryogenesis. The results revealed that the two genes are differentially expressed, in terms of both developmental stages and tissue distribution. In the majority of cases, fibrillin-2 transcripts appear earlier and accumulate for a shorter period of time than fibrillin-1 transcripts. Synthesis of fibrillin-1 correlates with late morphogenesis and the appearance of well-defined organ structures; fibrillin-2 synthesis, on the other hand, coincides with early morphogenesis and, in particular, with the beginning of elastogenesis. The findings lend indirect support to our original hypothesis stating that fibrillins contribute to the compositional and functional heterogeneity of the microfibrils. The available evidence is also consistent with the notion that the fibrillins might have distinct, but related roles in microfibril physiology. Accordingly, we propose that fibrillin-1 provides mostly force-bearing structural support, whereas fibrillin-2 predominantly regulates the early process of elastic fiber assembly.

In this work, switching dynamics of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer films are investigated over unprecedentedly wide ranges of temperature and electric field. Remarkably, domain switching of copolymer films obeys well the classical domain nucleation and growth model although the origin of ferroelectricity in organic ferroelectric materials inherently differs from the inorganic counterparts. A lower coercivity limit of 50 MV/m and 180° domain wall energy of 60 mJ/m2 are determined for P(VDF-TrFE) films. Furthermore, we discover in copolymer films an anomalous temperature-dependent crossover behavior between two power-law scaling regimes of frequency-dependent coercivity, which is attributed to the transition between flow and creep motions of domain walls. Our observations shed new light on the switching dynamics of semi-crystalline ferroelectric polymers, and such understandings are critical for realizing their reliable applications.

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