Comment on "Paramagnetic anomalies above the Curie temperature and colossal magnetoresistance in optimally doped manganites" - art. no. 106401

In a recently published paper [Phys. Rev. B 62, 5313 (2000)], Yuan et al. s tudied the magnetoresistance (MR) and electron paramagnetic resonance (EPR) of ceramic samples of (La1-xYx)(1/3)Ca2/3MnO3 (x = 0.15,0.20). They argue that the EPR linewidth and the MR exhibit similar temperature dependences i n the range T(c)less than or equal toT less than or equal toT(onset), and c onclude that the same mechanism underlies both effects. In our opinion,,the y made a mistake in analyzing the origin of EPR line broadening below T-ons et. Similar experiments carried out in single crystals showed that while th e peak of MR around T-C is intrinsic to these manganites, the observed line broadening is not. This effect has been previously related to the presence of pores between grains in polycrystalline samples and surface irregularit ies in single crystals, and is common to other magnetic materials that do n ot show colossal magnetoresistance.