Abstract
The impurity-induced antiferromagnetic ordering of the doped Haldane magnet was studied by electron-spin resonance (ESR) on ceramic samples in the frequency range 9–110 GHz. Below the Néel temperature a transformation of the ESR spectrum was found, indicating an antiferromagnetic-resonance mode of spin precession. The excitation gap of the spin-wave spectrum increases with increasing Mg concentration x in the same manner as the Néel temperature, reaching its maximum value of 80 GHz at . At small concentrations the signals of antiferromagnetic resonance were found to coexist with the signal of the paramagnetic resonance indicating a microscopic separation of the magnetic phases.
- Received 24 December 2001
DOI:https://doi.org/10.1103/PhysRevB.65.174422
©2002 American Physical Society