Electron Spin Resonance Above Tc In Layered Manganites

We have performed electron spin resonance (ESR) and dc magnetization measurements on single crystals of La2(1-x)Sr1+2xMn2O7 up to 800 K with special emphasis on the x = 0.4 composition. The ESR linewidth shows behavior similar to that observed in the three-dimensional perovskites and above ∼500 K can be described by a universal expression ΔHpp(T)=[C/Tχ(T)]ΔHpp (∞). The linewidth and the resonance field become anisotropic below ∼500 K. The anisotropy in the resonance field is proportional to the magnetization M, and we concluded that it is intrinsic to the system. We show that demagnetization effects can explain only part of the anisotropy. The remainder arises from short-range uniaxial terms in the Hamiltonian that are associated with the crystal field and Dzialozhinsky-Moriya interactions. The anisotropy in the linewidth is attributed to the easy-plane ferromagnetic ordering, which also arises from the short-range anisotropy.631717441311744136Ruddlesden, S.N., Popper, P., (1958) Acta Crystallogr., 11, p. 54Moritomo, Y., Asamitsu, A., Kuwahara, H., Tokura, Y., (1996) Nature (London), 380, p. 141Causa, M.T., Tovar, M., Caneiro, A., Prado, F., Ibanez, G., Ramos, C.A., Butera, A., Oseroff, S.B., (1998) Phys. Rev. B, 58, p. 3233Causa, M.T., Alejandro, G., Tovar, M., Pagliuso, P.G., Rettori, C., Oseroff, S.B., Subramanian, M.A., (1999) J. Appl. Phys., 85, p. 5408Huber, D.L., Alejandro, G., Caneiro, A., Causa, M.T., Prado, F., Tovar, M., Oseroff, S.B., (1999) Phys. Rev. B, 60, p. 12155Oseroff, S.B., Moreno, N.O., Pagliuso, P.G., Rettori, C., Huber, D.L., Gardner, J.S., Sarrao, J.L., Alascio, B.R., (2000) J. Appl. Phys., 87, p. 5810Seehra, M.S., Ibrahim, M.M., Babu, V.S., Srinivasan, G., (1996) J. Phys.: Condens. Matter, 8, p. 11283Dominguez, M., Lofland, S.E., Bhagat, S.M., Raychaudhuri, A.K., Ju, H.L., Venkates, T., Greene, R.L., (1996) Solid State Commun., 97, p. 193Lofland, S.E., Kim, P., Dahiroc, P., Bhagat, S.M., Tyagi, S.D., Karabashev, S.G., Shultyatev, D.A., Mukovskii, Y., (1997) Phys. Lett. A, 233, p. 476Kimura, T., Tomioka, Y., Kuwahara, H., Asamitsu, A., Tamura, M., Tokura, Y., (1996) Science, 274, p. 1698Perring, T.G., Aeppli, G., Moritomo, Y., Tokura, Y., (1997) Phys. Rev. Lett., 78, p. 3197Zhou, J.-S., Goodenough, J.B., Mitchell, J.F., (1998) Phys. Rev. B, 58, p. 579Zhou, J.-S., Goodenough, J.B., (1998) Phys. Rev. Lett., 80, p. 2665Kelley, T.M., Argyriou, D.N., Robinson, R.A., Nakotte, H., Mitchell, J.F., Osbron, R., Jorgensen, J.D., (1998) Physica B, 241-243, p. 439Heffner, R.H., MacLaughlin, D.E., Nieuwenhuys, G.J., Kimura, T., Luke, G.M., Tokura, Y., Uemura, Y.J., (1998) Phys. Rev. Lett., 81, p. 1706Potter, C.D., Swiatek, M., Bader, S.D., Argyriou, D.N., Mitchell, J.F., Miller, D.J., Hinks, D.G., Jorgensen, J.D., (1998) Phys. Rev. B, 57, p. 72Chauvet, O., Goglio, G., Molinie, P., Corraze, B., Brohan, L., (1998) Phys. Rev. Lett., 81, p. 1102Hirota, K., Moritomo, Y., Fujioka, H., Kubota, M., Yoshizawa, H., Endoh, Y., (1998) J. Phys. Soc. Jpn., 67, p. 3380Li, J.Q., Matsui, Y., Kimura, T., Tokura, Y., (1998) Phys. Rev. B, 57, pp. R3205Kimura, T., Kumai, R., Tokura, Y., Li, J.Q., Matsui, Y., (1998) Phys. Rev. B, 58, p. 11081Hayashi, T., Miura, N., Tokunaga, M., Kimura, T., Tokura, Y., (1998) J. Phys.: Condens. Matter, 10, p. 11525Suryanarayanan, R., Dhalenne, G., Revcolevschi, A., Prellier, W., Renard, J.P., Dupas, C., Caliebe, W., Chatterji, T., (2000) Solid State Commun., 113, p. 267Kubota, M., Fujioka, H., Ohoyama, K., Hirota, K., Moritomo, Y., Yoshizawa, H., Endoh, Y., (1999) J. Phys. Chem. Solids, 60, p. 116Bhagat, S.M., Lofland, S.E., Mitchell, J.F., (1999) Phys. Lett. A, 259, p. 326Kittel, C., (1997) Introduction to Solid State Physics, , Wiley, New YorkOkochi, M., (1970) J. Phys. Soc. Jpn., 28, p. 897Victoria, C., Barker, R.C., Yelon, A., (1967) Phys. Rev. Lett., 19, p. 792Nagata, K., (1976) J. Phys. Soc. Jpn., 40, p. 1209Nagata, K., Yamamoto, I., Takano, H., Yokozawa, Y., (1977) J. Phys. Soc. Jpn., 43, p. 857. , and references thereinHuber, D.L., Seehra, M.S., (1976) Phys. Status Solidi B, 74, p. 145Stanger, J.-L., Andre, J.-J., Turek, P., Hosokoshi, Y., Tamura, M., Kinoshita, M., Rey, P., Veciana, J., (1997) Phys. Rev. B, 55, p. 8398Van Vleck, J.H., (1950) Phys. Rev., 78, p. 266Kittel, C., (1948) Phys. Rev., 73, p. 15

Vibrational And Electronic Excitations In The (ce,la)m In5 (m=co,rh) Heavy-fermion Family

We present a systematic study at ambient pressure of the phononic and electronic Raman-active excitations in the ab plane of the (Ce,La)M In5 (M=Co,Rh) heavy-fermion family. We found that the characteristic Raman spectra of this family of compounds display two phonon modes at ∼38 and ∼165 cm-1 and a broad electronic background centered at ∼40 cm-1. For CeCoIn5, the temperature dependence of these excitations shows anomalous behavior near T* =45 K that may indicate a nontrivial renormalization of the electronic structure driven by strong correlations between hybridized 4f electrons. © 2007 The American Physical Society.754Heffner, R.H., Norman, M.R., (1996) Comments Condens. Matter Phys., 17, p. 361. , CCMPEB 0885-4483Anderson, P.W., (1961) Phys. Rev., 124, p. 41. , PHRVAO 0031-899X 10.1103/PhysRev.124.41Coqblin, B., Schrieffer, J.R., (1969) Phys. Rev., 185, p. 847. , PHRVAO 0031-899X 10.1103/PhysRev.185.847Rajan, V.T., (1983) Phys. Rev. Lett., 51, p. 308. , PRLTAO 0031-9007 10.1103/PhysRevLett.51.308Rossel, C., Yang, K.N., Maple, M.B., Fisk, Z., Zirngiebl, E., Thompson, J.D., (1987) Phys. Rev. B, 35, p. 1914. , See, for example, PRBMDO 0163-1829 10.1103/PhysRevB.35.1914Nakatsuji, S., Pines, D., Fisk, Z., (2004) Phys. Rev. Lett., 92, p. 016401. , PRLTAO 0031-9007 10.1103/PhysRevLett.92.016401Nakatsuji, S., Yeo, S., Balicas, L., Fisk, Z., Schlottmann, P., Pagliuso, P.G., Moreno, N.O., Thompson, J.D., (2002) Phys. Rev. Lett., 89, p. 106402. , PRLTAO 0031-9007 10.1103/PhysRevLett.89.106402Curro, N.J., Sarrao, J.L., Thompson, J.D., Pagliuso, P.G., Kos, Š., Abanov, At., Pines, D., (2003) Phys. Rev. Lett., 90, p. 227202. , PRLTAO 0031-9007 10.1103/PhysRevLett.90.227202Petrovic, C., Movshovich, R., Jaime, M., Pagliuso, P.G., Hundley, M.F., Sarrao, J.L., Fisk, Z., Thompson, J.D., (2001) Europhys. Lett., 53, p. 354. , EULEEJ 0295-5075 10.1209/epl/i2001-00161-8Petrovic, C., Pagliuso, P.G., Hundley, M.F., Movshovich, R., Sarrao, J.L., Fisk, Z., Thompson, J.D., (2001) J. Phys.: Condens. Matter, 13, p. 337. , JCOMEL 0953-8984 10.1088/0953-8984/13/17/103Sidorov, V.A., Nicklas, M., Pagliuso, P.G., Sarrao, J.L., Bang, Y., Balatsky, A.V., Thompson, J.D., (2002) Phys. Rev. Lett., 89, p. 157004. , PRLTAO 0031-9007 10.1103/PhysRevLett.89.157004Bianchi, A., Movshovich, R., Vekhter, I., Pagliuso, P.G., Sarrao, J.L., (2003) Phys. Rev. Lett., 91, p. 257001. , PRLTAO 0031-9007 10.1103/PhysRevLett.91.257001Bianchi, A., Movshovich, R., Capan, C., Pagliuso, P.G., Sarrao, J.L., (2003) Phys. Rev. Lett., 91, p. 187004. , PRLTAO 0031-9007 10.1103/PhysRevLett.91.187004Singley, E.J., Basov, D.N., Bauer, E.D., Maple, M.B., (2002) Phys. Rev. B, 65, p. 161101. , PRBMDO 0163-1829 10.1103/PhysRevB.65.161101Klein, M.V., (1983) Light Scattering in Solids I, 8, p. 147. , edited by M. Cardona, Topics in Applied Physics, Vol. Springer-Verlag, BerlinZawadowski, A., Cardona, M., (1990) Phys. Rev. B, 42, p. 10732. , PRBMDO 0163-1829 10.1103/PhysRevB.42.10732Menéndez, J., Cardona, M., (1984) Phys. Rev. B, 29, p. 2051. , PRBMDO 0163-1829 10.1103/PhysRevB.29.2051Harrison, N., (2004) Phys. Rev. Lett., 93, p. 186405. , PRLTAO 0031-9007 10.1103/PhysRevLett.93.186405Nayak, P., Ojha, B., Mohanty, S., Behera, S.N., (2002) Int. J. Mod. Phys. B, 16, p. 3595. , IJPBEV 0217-9792Hall, D., (2001) Phys. Rev. B, 64, p. 064506. , PRBMDO 0163-1829 10.1103/PhysRevB.64.064506Razafimandiby, H., Fulde, P., Keller, J., (1989) Z. Phys. B: Condens. Matter, 54, p. 111. , ZPCMDN 0722-3277 10.1007/BF01388062Christianson, A.D., (2004) Phys. Rev. B, 70, p. 134505. , PRBMDO 0163-1829 10.1103/PhysRevB.70.13450

Magnetic Structure Of Cerhin5 As A Function Of Pressure And Temperature

We report magnetic neutron-diffraction and electrical resistivity studies on single crystals of the heavy-fermion antiferromagnet CeRhIn5 at pressures up to 2.3 GPa. These experiments show that the staggered moment of Ce and the incommensurate magnetic structure change weakly with applied pressure up to 1.63 GPa, where resistivity, specific heat and nuclear quadrupole resonance measurements confirm the presence of bulk superconductivity. This work places important constraints on an interpretation of the relationship between antiferromagnetism and unconventional superconductivity in CeRhIn 5.692244031244036Heffner, R.H., Norman, M.R., (1996) Comments Condens. Matter Phys., 17, p. 361Stewart, G.R., (2001) Rev. Mod. 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Role of the E2g phonon in the superconductivity of MgB2: a Raman scattering study

Temperature dependent Raman scattering studies in polycrystalline MgB2(10<T<300 K)reveal that the E2g phonon does not experience any self energy renormalization effect across the superconducting critical temperature Tc ~ 40 K. In contrast, most of the current theoretical models rely on the role of the E2g phonon in the electron-phonon coupling mechanism of superconductivity in MgB2. According to these models, a hardening of 12% is expected below Tc at the Gamma point of the Brillouim zone. In the presence of our results, those models must be reviewed. The analysis of the temperature dependence of the E2g phonon frequency yields to a isobaric Gruneisen parameter of -1.2< gama(E2g)< 0.2, smaller than the value of 3.9 obtained from isothermal Raman experiments under pressure. It is suggested that this apparent disagreement can be explained in terms of pressure induced changes of the topology of the Fermi surface. Finally we notice that the phonon linewidth presents the expected two-phonon anharmonic decay as a function of T and no anomalous temperature dependence of the linewidth is observed near Tc.Comment: Published in Solid State Comm. 125, 499 (2003

The Orbital Order Parameter in La0.95Sr0.05MnO3 probed by Electron Spin Resonance

The temperature dependence of the electron-spin resonance linewidth in La0.95Sr0.05MnO3 has been determined and analyzed in the paramagnetic regime across the orbital ordering transition. From the temperature dependence and the anisotropy of linewidth and $g$-value the orbital order can be unambiguously determined via the mixing angle of the wave functions of the $e_{\rm g}$-doublet. The linewidth shows a similar evolution with temperature as resonant x-ray scattering results

Small-polaron hopping conductivity in bilayer manganite La1.2_{1.2}Sr1.8_{1.8}Mn2_{2}O7_{7}

We report anisotropic resistivity measurements on a La$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ single crystal over a temperature $T$ range from 2 to 400 K and in magnetic fields $H$ up to 14 T. For $T\geq 218$ K, the temperature dependence of the zero-field in-plane $\rho_{ab}(T)$ resistivity obeys the adiabatic small polaron hopping mechanism, while the out-of-plane $\rho_{c}(T)$ resistivity can be ascribed by an Arrhenius law with the same activation energy. Considering the magnetic character of the polarons and the close correlation between the resistivity and magnetization, we developed a model which allows the determination of $\rho_{ab,c}(H,T)$. The excellent agreement of the calculations with the measurements indicates that small polarons play an essential role in the electrical transport properties in the paramagnetic phase of bilayer manganites.Comment: 4 pages, 3 figures, to appear in Physical Review

Low-temperature electrical transport in bilayer manganite La1.2_{1.2}Sr1.8_{1.8}Mn2_{2}O7_{7}

The temperature $T$ and magnetic field $H$ dependence of anisotropic in-plane $\rho_{ab}$ and out-of-plane $\rho_{c}$ resistivities have been investigated in single crystals of the bilayer manganite La$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$. Below the Curie transition temperature $T_c=$ 125 K, $\rho_{ab}$ and $\rho_{c}$ display almost the same temperature dependence with an up-turn around 50 K. In the metallic regime (50 K $\leq T \leq$ 110 K), both $\rho_{ab}(T)$ and $\rho_{c}(T)$ follow a $T^{9/2}$ dependence, consistent with the two-magnon scattering. We found that the value of the proportionality coefficient $B_{ab}^{fit}$ and the ratio of the exchange interaction $J_{ab}/J_c$ obtained by fitting the data are in excellent agreement with the calculated $B_{ab}$ based on the two-magnon model and $J_{ab}/J_c$ deduced from neutron scattering, respectively. This provides further support for this scattering mechanism. At even lower $T$, in the non-metallic regime ($T<$ 50 K), {\it both} the in-plane $\sigma_{ab}$ and out-of-plane $\sigma_{c}$ conductivities obey a $T^{1/2}$ dependence, consistent with weak localization effects. Hence, this demonstrates the three-dimensional metallic nature of the bilayer manganite La$_{1.2}$Sr$_{1.8}$Mn$_{2}$O$_{7}$ at $T<T_c$.Comment: 7 pages and 5 figures, accepted for publication in Phys. Rev.

Spin Dynamics In Perovskites, Pyrochlores, And Layered Manganites

High temperature electron spin resonance (ESR) and magnetic susceptibility (χ) are analyzed for manganites related with colossal magnetoresistance (CMR). The properties of compounds with different crystalline structures: three-dimensional (3D) perovskites, pyrochlore, and La1.2Sr1.8Mn2O7, a two-dimensional layer, are compared. In the paramagnetic regime, and outside the critical regions associated with phase transitions, the temperature dependence of the ESR linewidth presents a universal behavior dominated by the variations of χ(T), ΔHpp(T) = [C/Tχ(T)]ΔHpp(∞). The high temperature limit of the linewidth, ΔHpp(∞), is related to the parameters of the Hamiltonian describing the interactions of the spin system. The role played by magnetic anisotropy, isotropic superexchange, and double exchange is revealed and discussed in the analysis of the experimental data. In CMR and non-CMR pyrochlores, ΔHpp(∞)∝ω2 p/J where J is proportional to the Curie-Weiss temperature, including the hybridization mechanism producing CMR. Instead, ΔHpp(∞) of CMR perovskites seems not to be affected by the double-exchange interaction. In contrast with the 3D perovskites, the ESR linewidth and resonance field of La1.2Sr1.8Mn2O7, a bilayer compound, although isotropic at high temperatures, becomes anisotropic for Tc= 125 K&lt;T&lt;Tp≈450 K. © 2000 American Institute of Physics.879 II58105812Causa, M.T., (1998) Phys. Rev. B, 58, p. 3233Lofland, (1997) Phys. Lett. A, 233, p. 476Causa, M.T., Alejandro, G., Tovar, M., Pagliuso, P.G., Rettori, C., Oseroff, S.B., Subramanian, M.A., (1999) J. Appl. Phys., 85, p. 5408Anderson, P.W., Weiss, P.R., (1953) Rev. Mod. Phys., 25, p. 269Zener, C., (1951) Phys. Rev., 82, p. 403Shimakawa, Y., Kubo, Y., Hamada, N., Jorgensen, J.D., Hu, Z., Short, S., Nohara, M., Takagi, H., (1999) Phys. Rev. B, 59, p. 1249. , and references thereinVentura, C., Alascio, B., (1997) Phys. Rev. B, 56, p. 14533Huber, D.L., Alejandro, G., Caneiro, A., Causa, M.T., Prado, F., Tovar, M., Oseroff, S.B., (1999) Phys. Rev. B, 60, p. 12155Chauvet, O., Goglio, G., Molinie, P., Corraze, B., Brohan, L., (1998) Phys. Rev. Lett., 81, p. 1102. , and references thereinMoreno, N.O., Pagliuso, P.G., Rettori, C., Gardner, J.S., Sarrao, J.L., Thompson, J.D., García-Flores, A., Oseroff, S.B., unpublishe

Small-scale magnetic buoyancy and magnetic pumping effects in a turbulent convection

We determine the nonlinear drift velocities of the mean magnetic field and nonlinear turbulent magnetic diffusion in a turbulent convection. We show that the nonlinear drift velocities are caused by the three kinds of the inhomogeneities, i.e., inhomogeneous turbulence; the nonuniform fluid density and the nonuniform turbulent heat flux. The inhomogeneous turbulence results in the well-known turbulent diamagnetic and paramagnetic velocities. The nonlinear drift velocities of the mean magnetic field cause the small-scale magnetic buoyancy and magnetic pumping effects in the turbulent convection. These phenomena are different from the large-scale magnetic buoyancy and magnetic pumping effects which are due to the effect of the mean magnetic field on the large-scale density stratified fluid flow. The small-scale magnetic buoyancy and magnetic pumping can be stronger than these large-scale effects when the mean magnetic field is smaller than the equipartition field. We discuss the small-scale magnetic buoyancy and magnetic pumping effects in the context of the solar and stellar turbulent convection. We demonstrate also that the nonlinear turbulent magnetic diffusion in the turbulent convection is anisotropic even for a weak mean magnetic field. In particular, it is enhanced in the radial direction. The magnetic fluctuations due to the small-scale dynamo increase the turbulent magnetic diffusion of the toroidal component of the mean magnetic field, while they do not affect the turbulent magnetic diffusion of the poloidal field.Comment: 13 pages, 4 figure, REVTEX4, Geophysical and Astrophysical Fluid Dynamics, in pres

Studies Of The Three-dimensional Frustrated Antiferromagnetic Zncr2o4

Results of studies of the susceptibility, magnetic specific heat, and electron paramagnetic resonance spectrum of the geometrically frustrated antiferromagnetic ZnCr2O4 are presented. The temperature dependence of the susceptibility and the specific heat are in good agreement with the predictions of the quantum tetrahedral mean field model for exchange-coupled spin-3/2 ions on a pyrochlore lattice. The origin of the anomalous behavior of the resonance intensity below 90 K is discussed. © 2001 American Institute of Physics.8911 II70507052Proceedings of the Conference Highly Frustrated Magnetism 2000 Can. J. Phys., , in pressRamirez, A.P., (1994) Annu. Rev. Mater. Sci., 24, p. 453Schiffer, P., Ramirez, A.P., (1996) Comments Condens. Matter Phys., 18, p. 21Kino, Y., Luthi, B., (1971) Solid State Commun., 9, p. 805Plumier, R., Lecomte, M., Sougi, M., (1977) J. Phys., 38, pp. L-149. , ParisLee, S.-H., Broholm, C., Kim, T.H., Ratcliff W. II, Cheong, S.-W., (2000) Phys. Rev. Lett., 84, p. 3718Martinho, H., cond-mat/0011171Garcia-Adeva, A.J., Huber, D.L., (2000) Phys. Rev. Lett., 85, p. 4598Baltzer, P.K., Wojtowicz, P.J., Robbins, M., Lopatin, E., (1966) Phys. Rev., 151, p. 367noteOhta, H., Okubo, S., Kikuchi, H., Ono, S., Proceedings of the Conference Highly Frustrated Magnetism 2000 Can. J. Phys., , in pressHuber, D.L., Alejandro, G., Caneiro, A., Causa, M.T., Prado, F., Tovar, M., Oseroff, S.B., (1999) Phys. Rev. B, 60, p. 1215