A ferroic material is basically a material which exhibits either ferroelectric or ferromagnetic or ferroelastic ordering, a feature typically demonstrated by the presence of a well defined hysteresis loop when the material is switched electrically, magnetically or mechanically. More recently there has been another ordering mechanism proposed which is called as ferrotoroidic ordering. Magnetoelectric coupling in the materials, on the other hand, is a more general phenomenon irrespective of the state of magnetic and electrical ordering. For example, it could occur in paraelectric ferromagnetic materials or it can be mediated by other parameter such as strain.

Hence, the term multiferroic would mean a material exhibiting two or more of the above ordering mechanisms. More recently, multiferroic materials have become of tremendous interests because of potential device applications. For example, one can have multi-state memory element or sensors which can be operated in multi-mode or spintronic devices. However, there are challenges in finding a material that would act as a perfect multiferroic. Most multiferroic materials are not naturally occurring and are made in the laboratory .There are problems with respect to their fabricability, while their transition temperatures are often impractical. Despite these challenges, research is on to find a material which would emerge as a potential device material. In this module we discuss some of the basic aspects of multiferroics and a few multiferroic materials.

The Module contains:

Suggested Reading:

• N. A. Hill, J. Phys. Chem. B, 104, 6694-6709 (2000)
  
  
• M. Fiebig, J. Phys. D: Appl. Phys., 38, R123–R152 (2005)
  
  
• W. Eerenstein, N. D. Mathur and J. F. Scott, Nature, 442, 759 (2006)