Giant magnetothermal conductivity and magnetostriction effect in the charge ordered Nd _0.8 Na _0.2 MnO ₃ compound

Abstract

We present results on resistivity (ρ), magnetization (M ), thermal conductivity (κ), magnetostriction ( ∆L L(0) ) and specific heat (C p ) of charge-orbital ordered antiferromagnetic Nd 0.8 Na 0.2 MnO 3 compound. Magnetic fieldinduced antiferromagnetic/charge-orbital ordered insulating to ferromagnetic metallic transition leads to giant magnetothermal conductivity and magnetostriction effect. The low-temperature irreversibility behavior in ρ, M , κ and ∆L L(0) due to field cycling together with striking similarity among the field and temperature dependence of these parameters manifest the presence of strong and complex spin-charge-lattice coupling in this compound. The giant magnetothermal conductivity is attributed mainly to the suppression of phonon scattering due to the destabilization of spin fluctuations and static/dynamic Jahn-Teller distortion by the application of magnetic field. Keywords: Magnetothermal conductivity, Magnetostriction and Metamagnetic transitionMagnetic-field-induced transitions in prototype correlated electron systems, where spin, charge, lattice, and orbital degrees of freedom are coupled strongly, have drawn a considerable attention due to their huge impact on physical properties. Such fascinating phenomena are usually observed in rare-earth based manganites close to half doping. Several field stimulated transitions viz., structural transition, first order to second order ferromagnetic (FM) transition and spin-flop metamagnetic transition from antiferromagnetic (AFM)/charge ordered (CO) state to FM state accompanied by insulator to metal transition have been extensively studied in divalent doped manganite. 1-5However, the study on monovalent hole-doped manganite systems is very much limited.6-10 The monovalent doping has the advantage of creation of optimum concentration of Mn 4+ ions with a relatively small level of doping, as compared to its divalent counterpart. Though there are few reports on the electronic transport, the heat transport and its correlation with magnetic and magnetoelastic properties need to be explored. Magnetothermal transport may provide important insights into carrier localization due to spin-fluctuations and Jahn-Teller (JT) distortion as a result of strong lattice coupling through the orbital degree of freedom.Recently, we have investigated the magnetic properties of a medium sized e g electron bandwidth CO system Nd 1−x Na x MnO 3 , 6 where the quenching of CO phase was achieved at a lower field relative to other narrowband manganites.1,4 Repaka et al. 10 have observed giant magneto-thermoelectric power in a quite similar compound and suggested a close interplay between magnetization, electrical resistance and thermoelectric power. In order to understand the nature and strength of spin-lattice coupling and JT distortion and their role on transport properties, we have carried out temperature and field dependence of resistivity (ρ), magnetization (M ), thermal conductivity (κ), magnetostriction ( ∆L L(0) ) and specific heat (C p ) a) Electronic mail: prabhat.m...

Heat switch effect in an antiferromagnetic insulator Co3V2O8

“…10 (ii) Other less important effects on phonon transport could be related to the magnetoelastic coupling or magnetostriction effect. 33 Second, the magnetic scattering of phonons is weak at subkelvin temperatures. It can be seen from Debye formula that the phonon scattering rate is dominated by the boundary scattering.…”