Observation of fractional spin<i>S</i>=1/2 on open ends of<i>S</i>=1 linear antiferromagnetic chains: Nonmagnetic doping

Abstract

Approximately 0.5% of nonmagnetic divalent ions Zn, Cd, and Hg have been alternatively substituted for Ni in the linear chain of antiferromagnetically coupled ${\mathrm{Ni}}^{2+}$ (S=1) spins in [Ni(${\mathrm{C}}_{2}$${\mathrm{H}}_{8}$${\mathrm{N}}_{2}$${)}_{2}$(${\mathrm{NO}}_{2}$)]${\mathrm{CIO}}_{4}$ (NENP). While at low temperature the pure NENP shows no EPR signal, the doped NENP shows identical EPR spectra corresponding to the fractional spin S=1/2 states at the ``open'' ends of the Ni chains adjacent to the nonmagnetic substitutions.