Magnetic properties of a ferrimagnetic mixed (1,3/2) spin chain with inhomogeneous crystal-field anisotropy

There are many magnetic materials which behave as low dimensional compounds. One of the nice macroscopic manifestations of quantum mechanics in these materials is the apperance of plateaux in the magnetization curve.

I was attracted by the origin of the rare case of antiferromagnetism between the Ni(II) and Cr(III) ions — with spins $s=1$ and $S=3/2$ respectively — in the quasi-one-dimensional heterotrinuclear complex [NiCr$_2$(bipy)$_2$(C$_2$O$_4$)$_4$(H$_2$O)$_2$]H$_2$O. So I decided to study a simple yet informative model of a spin chain with Ising interactions and anisotropies in the crystal fields of alternating spins $(s,S)=(1,3/2)$.

By bringing the Molecular Field Theory to this problem, together with Density Matrix Renormalization Group (DMRG) studies, I was able to understand the magnetization curve (with plateaux) in this model, as well as the phase diagram and configurations of lowest energy.