Field-Induced Local Excitations Causing Zero-Magnetization Plateaus in Antiferromagnets of Antiferromagnetic Spin Dimers Under Magnetic Field

Certain antiferromagnets composed of antiferromagnetic spin dimers exhibit a zero-magnetization plateau despite that the single-ion anisotropy of their magnetic ions is negligible. The cause for this observation was investigated by analyzing how a magnetic field affects the energy spectrum of an antiferromagnetic chain composed of antiferromagnetic spin dimers made up of two spin-half ions and by carrying out specific heat measurements for potassium copper chloride as a function magnetic field at 2 K.