Magnetic properties of delta- and kagome-like chains with competing interactions

We study the delta-chain with spin-$1$ on basal sites and spin-$\frac{1}{2}$ on apical sites. The Heisenberg interaction between neighbor basal spins is antiferromagnetic (AF) and the interaction between basal and apical spins is ferromagnetic (F). We show that the magnetization curve of this model is the same as that of the spin-$\frac{1}{2}$ kagome-like chain with competing Heisenberg interactions. The ground state phase diagram of the latter as a function of the ratio between the AF and F interaction, $\alpha $, consists of the ferromagnetic, ferrimagnetic and singlet phases. We study the magnetic properties in each ground state phase and analyze the magnetization curves. We show that there are magnetization plateaus and jumps in definite regions of value $\alpha$. We compare the magnetic properties of considered models with those of the spin-$\frac{1}{2}$ delta chain.
Comment: 20 pages, 9 figures