ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
An analysis is given of recent electron paramagnetic resonance (EPR) experiments in manganite materials displaying colossal magnetoresistance behavior. These experiments have established that in highly homogeneous samples characterized by a single resonance line, the EPR linewidths above the critical region associated with the paramagnetic–ferromagnetic transition are inversely proportional to Tχ(T), where χ denotes the susceptibility. This behavior indicates that the linewidth does not reflect a coupling to the lattice vibrations but rather is caused by a spin-only mechanism. The possibility that the linewidth arises from the dipolar interaction is assessed using an effective interaction model. On the basis of the model calculation, it is concluded that the dipolar interaction is probably too weak to account for the observed broadening and that the linewidth most likely arises from tetragonal and orthorhombic distortions of the octahedral crystal field at the sites of the Mn ions. The EPR linewidth in samples with very low concentrations of Mn4+ ions is expected to vary with temperature as [Tχsp(T)]−1, where χsp(T) is the susceptibility of the ferromagnetically coupled spin polaron. By measuring the temperature dependence of the linewidth, one may be able to determine the temperature dependence of the polaron susceptibility. © 1998 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.367538
