Why study insulators?

author: James F. Scott, Cavendish Laboratory, University of Cambridge
published: May 6, 2009,   recorded: March 2009,   views: 6773

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Superconductors are sexier and semiconductors produce a billion $ per year in devices. So why should scientists study insulating materials? Firstly, most magnets are insulators; and second, all ferroelectrics (which switch charge in an applied voltage) are insulators. So phenomena that involve magnetism or ferroelectricity (piezoelectricity and pyroelectricity) are generally insulating. In the past few years the study of insulating materials has taken two new directions: The study of nano-devices, including sensors, actuators, and transducers. The first thing one discovers is that if you make an insulating material thin enough, it conducts quite well. And what are the conduction mechanisms: Poole-Frenkel, Schottky, Fowler-Nordheim tunneling, space-chage-limited? The second thing one finds is that ferroelectrics and ferromagnets have domains -- and the smaller the object, the smaller its domains. We have developed a theory of nano-domains that works in all magnets and ferroelectrics from 2 nm in size to 2 mm -- six orders of magnitude -- with no adjustable parameters. We also find domains that are round instead of rectangular and fractal instead of integer in dimension. Finally, I will talk about materials that are simultaneously magnetic and ferroelectric. Gilbert showed in 1600 that electrostatics and magnetism are unrelated -- but that isn't quite true. If time permits I will show some ferroelectric memories, including the ones in the SONY Playstation.

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