Comment on ``Paramagnetic anomalies above the Curie temperature and colossal magnetoresistance in optimally doped manganites''
Abstract
In a recently published paper [Phys. Rev. B 62, 5313 (2000)], Yuan et al. studied the magnetoresistance (MR) and electron paramagnetic resonance (EPR) of ceramic samples of (La1-xYx)1/3Ca2/3MnO3 (x=0.15,0.20). They argue that the EPR linewidth and the MR exhibit similar temperature dependences in the range TC<=T<=Tonset, and conclude that the same mechanism underlies both effects. In our opinion, they made a mistake in analyzing the origin of EPR line broadening below Tonset. Similar experiments carried out in single crystals showed that while the peak of MR around TC 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 irregularities in single crystals, and is common to other magnetic materials that do not show colossal magnetoresistance.
- Publication:
-
Physical Review B
- Pub Date:
- September 2001
- DOI:
- 10.1103/PhysRevB.64.106401
- Bibcode:
- 2001PhRvB..64j6401R
- Keywords:
-
- 76.30.-v;
- 75.30.Vn;
- 76.50.+g;
- 71.30.+h;
- Electron paramagnetic resonance and relaxation;
- Ferromagnetic antiferromagnetic and ferrimagnetic resonances;
- spin-wave resonance;
- Metal-insulator transitions and other electronic transitions