Indian Institute of Science Education and Research

Dr. V. Ravi Chandra

Physics Department Technion - Israel Institute of Technology Haifa 32000, Israel

The study of the effects of competing interactions, more commonly called
"frustration", is one of the important themes in research on magnetic systems.
In this talk I will present some aspects of this diverse subject using my work
on a selection of lattice models.
I will begin with a study of the ground state phase diagram of a frustrated
mixed-spin ladder with spin-1/2 and spin-1 rungs alternating with each other.
Frustration induces phase transitions between four different ground
states : two paramagnetic and two different partially magnetised phases.
In a closely related model with all spins the same, I will demonstrate the
existence of (exactly solvable) magnetisation plateaus connected by
jumps which appear through an interplay of frustration and a magnetic
field. Finally, I will discuss our ongoing efforts to study the spin-1/2
nearest neighbour antiferromagnet on the Kagome lattice using Contractor
Renormalisation (CORE). I will outline the technical challenges involved
in using a large (12 site) building block and present a method to compute
the spectra of reasonably large system sizes (up to 36 spin-1/2 sites)
with modest computational resources.