OPOMNIK: IJS KOLOKVIJ, 26. 3. 2009 ob 13:00, prof. James F. Scott

[Andreja Berglez]

Vabim vas na 13. predavanje iz sklopa "Kolokviji na IJS" v letu 2008/09, v
okviru Stefanovih dnevov, ki bo v četrtek, 26. marca 2009, ob 13:00 uri v
Veliki predavalnici Instituta >Jožef Stefan< na Jamovi cesti 39 v Ljubljani.
Napovednik predavanja najdete tudi na naslovu
http://www.ijs.si/ijsw/Koledar_prireditev, posnetke preteklih predavanj pa
na http://videolectures.net/kolokviji_ijs. 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



Prof. James F. Scott

Department of Physics, Cavendish Laboratory, Cambridge, University, Velika
Britanija

 

 

Zakaj moramo študirati tudi izolatorje?

 

Superprevodniki so zelo atraktivni materiali, polprevodniki pa so milijardni
posel. Zakaj naj bi torej znanstveniki sploh študirali izolatorje? Najprej,
večina magnetnih materialov je izolatorskih. Drugič, tudi vsi feroelektriki
so izolatorji. Torej, materiali, kjer najdemo hkrati magnetne in
feroelektrične lastnosti so po definiciji izolatorji. V preteklih letih so
raziskave izolatorskih materialov ubrale nove poti: študij naprav
nanometrskih dimenzij, vključno s senzorji, aktuatorji ter pretvorniki.
Prvo, kar lahko opazimo, je, da ko napravimo izolator dovolj tanek, začne
dobro prevajati. Kateri je torej mehanizem prevajanja: Poole-Frenkelovo,
Schottkyjevo ali Fowler-Nordheimovo tuneliranje? Drugič, feroelektriki in
feromagneti imajo domene - čim manjši je vzorec, tem manjše so domene. V
naši skupini smo razvili teorijo, ki dobro opiše vedenje feromagnetnih in
feroelektričnih materialov dimenzij med 2 nm in 2 mm - torej obseg 6 redov
velikosti - brez kakršnih koli prostih parametrov. Odkrili smo, da so domene
zaokrožene in fraktalne. Na koncu se bomo posvetili materialom, ki so hkrati
magnetni in feroelektrični. Gilbert je leta 1600 pokazal, da sta
elektrostatika in magnetizem nepovezana. Vendar to ni čisto res! Pokazali
bomo nekaj feroelektričnih spominskih elementov, vključno s tistimi, ki so
vgrajeni v SONY Playstation.

 

Predavanje bo v angleščini.

 
Lepo vabljeni!
 

***

 

We would like to invite you to 13th lecture of the "Kolokvij na IJS" ("Days
of Jožef Stefan") in the school year 2008/09. The lecture will be held on
Thursday, Mar 26 2009, at 1 pm at JSI main lecture hall, Jamova 39,
Ljubljana. The abstract of the lecture can be found on website:
<http://www.ijs.si/ijsw/Koledar_prireditev>
http://www.ijs.si/ijsw/Koledar_prireditev, the previous recorded lectures
can be found on website:  <http://videolectures.net/kolokviji_ijs>
http://videolectures.net/kolokviji_ijs. 

********************************************



 

Prof. James F. Scott 

Department of Physics, Cavendish Laboratory, Cambridge University, UK

 

Why study insulators?

 

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.

 

 

We look forward to meeting you at the "Kolokvij na IJS"!

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.ijs.si/pipermail/kolokvij-ijs/attachments/20090326/e051ec26/attachment.html>