2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/30013The zero-temperature magnetization process of a one-dimensional S=1/2 spin system with next-nearest-neighbour coupling alpha and anisotropy delta is studied. There is a region in the parameter space where the magnetization has a jump at certain external field. The boundary of this region is determined. The two cases are distinguished according as alpha<1/4 or alpha>1/4. In the latter case, the energy dispersion of the low-lying excitations exhibits a double minimum structure.4 pages, 7 eps figures, uses jpsj.styStrongly Correlated ElectronsStatistical Mechanicstext