Research Projects

A material exhibiting the co-existence and coupling of any of the two order parameters viz., magnetic, ferroelectric and ferroelastic are known as multiferroic materials. If the ferroelectricity originated by the certain arrangement of magnetic order (by-product of magnetic transition), then such spin driven ferroelectricity is known as type-II multiferrocity. Previously known to be a low temperature phenomenon; such strong magneto-electric materials are now gaining attention in the light of recent works, which reports that these spin driven ferroelectricity can be tuned near the room temperature. The most acceptable approach in this regard is strain engineering. The sample under consideration, Tb₂BaNiO₅, is Haldane quantum spin chain, in which we have recently discovered type-II multiferrocity. It consists of two antiferromagnetic transition (T₁= 63 K and T₂= 25 K), and the lower magnetic transition (T₂) is also ferroelectric transition. Tb₂BaNiO₅ shows huge magneto-dielectric coupling and the neutron measurements suggests that the canting angle of a pair of spins (Ni 3d and Tb 4f) determines the onset of magneto-electric coupling. Essentially Tb₂BaNiO₅, consist of rich physics, but for application point of view, it is not feasible due to low temperature constraint. Therefore, preparation of strained thin films is worthwhile to explore in such class of materials. With strain engineering, there is possibilities of tuning the ferroelectricity, thus multiferroicity, close to room temperature. For better understanding of the origin of such spin-driven ferroelectricity, detailed neutron and XAFS measurements are also planned in the current project. So overall, preparation and characterization of the epitaxial thin film of Tb₂BaNiO₅ essentially help us, not only to tune its functional properties close to room temperature, but also to explore rich physics associated with it.