Interplay of alternation and further neighbor interactions in S-1/2 spin chain Ca2CuAl4O8

Spin chains provide a testing ground for concepts in quantum magnetism. No long-range magnetic order is expected, while gapless fractional spinons excitations are predicted for spin-1/2 ions. In the case where the interactions alternate along a spin-1/2 chain the alternation confines the spinons resulting in gapped magnons. The introduction of second neighbor interactions provides another way to modify spin chains. Antiferromagnetic second neighbor interactions compete with the first neighbour interactions and exotic phases are expected such as spin-multipolar phases and nematic states in high magnetic field. Here we propose to investigate a new compound that combines alternating ferromagnetic – antiferromagnetic first neighbor interactions with stronger antiferromagnetic second neighbor interactions and is a candidate compound for nematic order in a magnetic field.