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Spin Dynamics of the Magnetoresistive Pyrochlore Tl_2Mn_2O_7

J. W. Lynn·L. Vasiliu-Doloc·M. A. Subramanian
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Abstract

Neutron scattering has been used to study the magnetic order and spin dynamics of the colossal magnetoresistive pyrochlore Tl_2Mn_2O_7. On cooling from the paramagnetic state, magnetic correlations develop and appear to diverge at T_C (123 K). In the ferromagnetic phase well defined spin waves are observed, with a gapless ($Δ<0.04$ meV) dispersion relation E=Dq^{2} as expected for an ideal isotropic ferromagnet. As T approaches T_C from low T, the spin waves renormalize, but no significant central diffusive component to the fluctuation spectrum is observed in stark contrast to the La$_{1-x}$(Ca,Ba,Sr)$_x$MnO$_3$ system. These results argue strongly that the mechanism responsible for the magnetoresistive effect has a different origin in these two classes of materials.

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J. W. Lynn, L. Vasiliu-Doloc, M. A. Subramanian. 1998-05-11. Spin Dynamics of the Magnetoresistive Pyrochlore Tl_2Mn_2O_7. https://doi.org/10.1103/physrevlett.80.4582

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