> Date: Fri, 22 Aug 1997 13:58:46 -0400 > From: Mike > Subject: Re: Smart cards - FerroElectric - Aye ? > > At 11:12 AM 8/22/97 -0700, you wrote: > > >Which is EXACTLY why we DON'T rely on EEPROM; we use FRAM! Ferroelectric > >RAM (there's nothing magnetic about it, folks, the ``ferro'' moniker is > >historical accident) is batteryless nonvolatile RAM which writes and reads > >as fast and low power as SRAM. > > Aye ? Doesn't the memory cell exploit a valence change of a bound Fe atom ? > > Rgds > > Mike > Perth, Western Australia No valence, no Fe, no iron, no magnetism. Ramtron's current material is based on lead zirconate titanate: ``PZT'', in the form of a Perovskite crystaline layer. The ferroelectric effect has a hysteresis curve that resembles magnetism, and thus the name. But the physical basis is the ability to trap a tetra- or pentavalent atom in one or the other of two stable positions (imagine two Cheops' pyramids stuck base-to-base, and a suitibly immense beachball which wants to be in the middle of a pyramid -- either one, but no place else); either position creates a polarized capacitance: not a stored charge, but a difference in capacity to store charge. They are electric (or electrostatic) dipoles, not magnetic ones, which you can set in either direction. [Disclaimer: I'm not a physicist, and a certain amount of this is repeated without full understanding. But it's not magnetic!] Peter F. Klammer, Racom Systems Inc. PKlammer@ACM.Org 6080 Greenwood Plaza Boulevard (303)773-7411 Englewood, CO 80111 FAX:(303)771-4708