u‰‰ŽาF Karlo Penc ŽiResearch Institute for Solid State Physics and Optics of the Hungarian Academy of Sciencesj “๚ŽžF @‚RŒŽ‚P‚V“๚i–ุj@Œ฿Œใ‚SŽž‚R‚O•ช‚ฉ‚็ ๊ŠF ยŽRŠw‰@‘ๅŠw@—HŠw•”i‘Š–อŒดƒLƒƒƒ“ƒpƒXj‚k“‚UŠK@‚k‚U‚O‚RŽบ ‘่–ฺFuHalf-magnetization plateau stabilized by structural distortion in the antiferromagnetic Heisenberg model on a pyrochlore latticev —vŽ|F Magnetization plateaus, visible as anomalies in magnetic susceptibility at low temperatures, are one of the hallmarks of frustrated magnetism. We show how an extremely robust half-magnetization plateau can arise from coupling between spin and lattice degrees of freedom in a pyrochlore antiferromagnet, and develop a detailed symmetry of analysis of the simplest possible scenario for such a plateau state. The application of this theory to the spinel oxides CdCr2O4 and HgCr2O4,where a robust half magnetization plateau has been observed, is discussed. --------------------------------- ‹ครF@ยŽRŠw‰@‘ๅŠw@—HŠw‰๏