Zernike Institute for Advanced Materials Colloquium Nicola Spaldin
|01 november 2007||FWN-Building 5111.0080, Nijenborgh 4, 9747 AG, Groningen|
|Speaker:||Prof. Dr. Nicola Spaldin|
|Affiliation:||Materials Department, University of California, Santa Barbara, USA|
|Date:||Thu Nov 1, 2007|
|Start:||16.00 (Doors open and coffee available at 15.30)|
There has been tremendous recent interest in multifunctional or "smart" materials, such as piezoelectrics, magnetostrictive materials, shape memory alloys, and piezomagnets, to name a few. Such materials find widespread and diverse applications, for example in medical ultrasound devices, smart structures in automobiles, naval sonar and micromachines, however the fundamental physics behind their functionality is often poorly understood. Of particular interest, both from a basic scientific and an applications perspective are materials that combine pairs of contraindicated functionalities, such as ferromagnetism and ferroelectricity. Such "multiferroics" have a spontaneous magnetization which can be switched by an applied magnetic field, a spontaneous polarization which can be switched by an applied electric field, and often some coupling between the two. Here we use the study of multiferroics to illustrate how modern computational and theoretical tools can provide invaluable basic insight into functional behavior, and in turn enable the development of new device paradigms based on combinations of functionalities. First we determine the fundamental physics behind the scarcity of ferromagnetic ferroelectric coexistence, and show that in general the transition metal d electrons, which are essential for magnetism, reduce the tendency for off-center polar distortions. Then we identify the chemistry behind the additional electronic or structural driving forces that must be present for ferromagnetism and ferroelectricity to occur simultaneously.
Finally we describe the successful rational design and subsequent synthesis of some new multiferroic materials and outline some of the many exciting avenues for further work in the field.
|Laatst gewijzigd:||22 oktober 2012 14:30|