Pyrochlore Manganites Spin Dynamics In The Paramagnetic Regime

Abstract

We report electron spin resonance (ESR) and dc magnetic susceptibility in polycrystalline pyrochlores A2Mn2O7 (A=Y, Tl) measured in the paramagnetic phase up to 600 K. It is shown that the ESR linewidth has a universal behavior given by ΔHpp(T) = ΔHpp(T→∞)[C/Tχdc(T)], where C is the single-ion Curie constant. The high-temperature limit for the linewidth, given by ΔHpp(T→∞)∝(ωp)2/J, is determined by the superexchange constant J for each material. A value of (ωp/γ) = 6300 G was found for all pyrochlores, including In2Mn2O7. Different broadening mechanisms are discussed. © 1999 American Institute of Physics.858 II B54085410Jin, S., Tiefeid, T.H., McCormack, M., Fastnach, R.A., Ramesh, R., Chen, L.H., (1994) Science, 264, p. 413Millis, A.J., Littlewood, P.B., Shraiman, B.I., (1995) Phys. Rev. Lett., 74, p. 5144Allub, R., Alascio, B., (1997) Phys. Rev. B, 55, p. 14113Rettori, C., Rao, D., Singley, J., Kidwell, D., Oseroff, S.B., Causa, M.T., Neumeier, J.J., Schultz, S., (1997) Phys. Rev. B, 55, p. 3083Granado, E., Pagliuso, P.G., Sanjurjo, J.A., Rettori, C., Oseroff, S.B., Causa, M.T., Butera, A., Rivas, J., (1998) Non-Crystalline and Nanoscale Materials, pp. 105-115. , edited by J. Rivas and M. A. López-Quintela World Scientific, SingaporeCausa, M.T., (1998) Phys. Rev. B, 58, p. 3233Tovar, M., (1998) J. Appl. Phys., 83, p. 7201Rosenfeld, H.D., Subramanian, M.A., (1996) J. Solid State Chem., 125, p. 278Subramanian, M.A., Torardi, C.C., Johnson, D.C., Pannetier, J., Sleight, A.W., (1988) J. Solid State Chem., 72, p. 24Reimers, J.N., Greedan, J.E., Kremer, R.K., Gmelin, E., Subramanian, M.A., (1991) Phys. Rev. B, 43, p. 3387Raju, N.P., Greedan, J.E., Subramanian, M.A., (1994) Phys. Rev. B, 49, p. 1086Hwang, H.Y., Cheong, S.-W., (1997) Nature (London), 389, p. 942Ventura, C., Alascio, B., (1997) Phys. Rev. B, 56, p. 14533Kennedy, B.J., (1998) Physica B, 241-243, p. 303Cox, D., private communicationSeehra, M.S., (1968) Rev. Sci. Instrum., 39, p. 1044Anderson, P.W., Weiss, P.R., (1953) Rev. Mod. Phys., 25, p. 269Huber, D.L., (1998) J. Appl. Phys., 83, p. 6949Huber, D.L., Causa, M.T., Tovar, M., private communicationCausa, M.T., Alejandro, G., Zysler, R., Prado, F., Caneiro, A., Tovar, M., J. Magn. Magn. Mater., , in pres