Comment on 'Visualizing high-temperature spin dynamics in La _1-xCa_xMnO₃ from a mapping of EPR linewidth and g factor'

In a recent paper (Liu et al 2007 J. Phys.: Condens. Matter 19 196213), Liu et al reported measurements of the electron paramagnetic resonance (EPR) of polycrystalline La_1-xCa_xMnO₃ (LCMO) manganites, and a study of the temperature and concentration (x) dependences of the EPR signal parameters. In particular, the authors claimed notable asymmetry of the paramagnetic (PM) linewidth ΔH_pp and g factor versus x. It is suggested in this comment that such a claim seems to be wrong as regards the PM g factor for the LCMO system. The reason for the above noted invalid conclusion of Liu et al may be the use of an inadequate method for extracting PM g factor values. It is noted that real electron-hole doping asymmetry manifests itself in, e.g., low-temperature behavior of the resonance signal intensity in accordance with the LCMO phase diagram. Numerous uncertainties and obscurities are also characteristic of the paper commented on.