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Influence of spin fluctuations on the superconducting transition temperature and resistivity in the t-J model at large N  [PDF]
A. Greco,R. Zeyher
Physics , 2000, DOI: 10.1103/PhysRevB.63.064520
Abstract: Spin fluctuations enter the calculation of the superconducting transition temperature T$_c$ only in the next-to-leading order (i.e., in O(1/N$^2$) of the 1/N expansion of the t-J model. We have calculated these terms and show that they have only little influence on the value of T$_c$ obtained in the leading order O(1/N) in the optimal and overdoped region, i.e., for dopings larger than the instability towards a flux phase. This result disagrees with recent spin-fluctuation mediated pairing theories. The discrepancies can be traced back to the fact that in our case the coupling between electrons and spins is determined by the t-J model and not adjusted and that the spin susceptibility is rather broad and structureless and not strongly peaked at low energies as in spin-fluctuation models. Relating T$_c$ and transport we show that the effective interactions in the particle-particle and particle-hole channels are not simply related within the 1/N expansion by different Fermi surface averages of the same interactin as in the case of phonons or spin fluctuations. As a result, we find that large values for T$_c$ and rather small scattering rates in the normal state as found in the experiments can easily be reconciled with each other. We also show that correlation effects heavily suppress transport relaxation rates relative to quasiparticle relaxation rates in the case of phonons but not in the case of spin fluctuations.
Phase coexistence and resistivity near the ferromagnetic transition of manganites  [PDF]
A. S. Alexandrov,A. M. Bratkovsky,V. V. Kabanov
Physics , 2006, DOI: 10.1103/PhysRevLett.96.117003
Abstract: Pairing of oxygen holes into heavy bipolarons in the paramagnetic phase and their magnetic pair-breaking in the ferromagnetic phase [the so-called current-carrier density collapse (CCDC)] has accounted for the first-order ferromagnetic phase transition, colossal magnetoresistance (CMR), isotope effect, and pseudogap in doped manganites. Here we propose an explanation of the phase coexistence and describe the magnetization and resistivity of manganites near the ferromagnetic transition in the framework of CCDC. The present quantitative description of resistivity is obtained without any fitting parameters by using the experimental resistivities far away from the transition and the experimental magnetization, and essentially model independent.
Magnetic Phase Diagram and Metal-Insulator Transition of NiS2-xSex  [PDF]
M. Matsuura,H. Hiraka,K. Yamada,Y. Endoh
Physics , 2000, DOI: 10.1143/JPSJ.69.1503
Abstract: Magnetic phase diagram of NiS2-xSex has been reexamined by systematic studies of electrical resistivity, uniform magnetic susceptibility and neutron diffraction using single crystals grown by a chemical transport method. The electrical resistivity and the uniform magnetic susceptibility exhibit the same feature of temperature dependence over a wide Se concentration. A distinct first order metal-insulator (M-I) transition accompanied by a volume change was observed only in the antiferromagnetic ordered phase for 0.50
Sr$_2$IrO$_4$ magnetic phase diagram, from resistivity  [PDF]
L. Fruchter,G. Collin,D. Colson,V. Brouet
Physics , 2014,
Abstract: We show that, contrary to previous belief, the transition to the antiferromagnetic state of Sr$_2$IrO$_4$ in zero magnetic field does show up in the transverse resistivity. We attribute this to a change in transverse integrals associated to the magnetic ordering, which is evaluated considering hopping of the localized charge. The evolution of the resistivity anomaly associated to the magnetic transition under applied magnetic field is studied. It tracks the magnetic phase diagram, allowing to identify three different lines, notably the spin-flip line, associated with the reordering of the ferromagnetic component of the magnetization, and an intriguing line for field induced magnetism, also corroborated by magnetization measurements.
Detecting percolative metal-insulator transition in manganites by resistive relaxation  [PDF]
X. J. Chen,H. -U. Habermeier,C. C. Almasan
Physics , 2003,
Abstract: We report an experimental study of the time dependence of resistivity of a La$_{0.9}$Sr$_{0.1}$MnO$_{3}$ ultrathin film in order to elucidate the underlying mechanism for metal-insulator transition and colossal magnetoresistance CMR effect. There is a clear change of sign in the resistive relaxation rate across the metal-insulator transition driven by temperature or magnetic field. When measuring in increasing temperature or decreasing magnetic field, the resistivity increases with time in the metallic state but decreases with time in the insulating state. These relaxation processes indicate that the metal-insulator transition and the associated CMR are a direct result of phase separation and of percolation of the metallic phase.

Chen Peng,Du You-wei,

中国物理 B , 2001,
Abstract: The magnetocaloric effect in polycrystalline of Pr1-xSrxMnO3 (x=0.33, 0.43, 0.50) has been investigated. A large magnetic entropy change (7.1J/kgK) was discovered in Pr0.5Sr0.5MnO3 under a low magnetic field of 1T at charge-ordered state transition temperature (161K). The physical mechanism is related to a drastic magnetization change at a temperature where the field-induced magnetic, electron and structural phase transitions occur (from the antiferromagnetic charge-ordered state to the ferromagnetic charge-disordered state).
Inelastic contribution of the resistivity in the hidden order in URu2Si2  [PDF]
E Hassinger,T D Matsuda,G Knebel,V Taufour,D Aoki,J Flouquet
Physics , 2010, DOI: 10.1088/1742-6596/273/1/012031
Abstract: In the hidden order of URu2Si2 the resistivity at very low temperature shows no T^2 behavior above the transition to superconductivity. However, when entering the antiferromagnetic phase, the Fermi liquid behavior is recovered. We discuss the change of the inelastic term when entering the AF phase with pressure considering the temperature dependence of the Grueneisen parameter at ambient pressure and the influence of superconductivity by an extrapolation of high field data.

YUAN Ning-Yi,LI Jin-Hu,LI Ge,

红外与毫米波学报 , 2004,
Abstract: Based on the model of the two phases of grain and grain boundary, the grain boundary tunneling of carriers was considered to simulate the change of the resistivtiy of VO2 polycrystalline film prepared by Sol-gel method in temperature range of 10℃~100℃.The simulation results were in good agreement with the experiment data. The results indicate that the grain boundary effect decreases the magnitude of resistivity change of VO2 film durying semiconductor-to-metal phase transition, and meanwhile the VO 2 film in metal phase has a negative temperature coefficient of resistivity.
Molecular Beam Epitaxy of LiMnAs  [PDF]
V. Novak,M. Cukr,Z. Soban,T. Jungwirth,X. Marti,V. Holy,P. Horodyska,P. Nemec
Physics , 2010, DOI: 10.1016/j.jcrysgro.2010.11.077
Abstract: We report on the molecular beam epitaxy (MBE) growth of high crystalline quality LiMnAs. The introduction of a group-I alkali metal element Li with flux comparable to fluxes of Mn and As has not caused any apparent damage to the MBE system after as many as fifteen growth cycles performed on the system to date.
Peculiar behavior of the electrical resistivity of MnSi at the ferromagnetic phase transition  [PDF]
Alla E. Petrova,Eric Bauer,V. Krasnorussky,Sergei M. Stishov
Physics , 2006, DOI: 10.1103/PhysRevB.74.092401
Abstract: The electrical resistivity of a single crystal of MnSi was measured across its ferromagnetic phase transition line at ambient and high pressures. Sharp peaks of the temperature coefficient of resistivity characterize the transition line. Analysis of these data shows that at pressures to ~0.35 GPa these peaks have fine structure, revealing a shoulder at ~ 0.5 K above the peak. It is symptomatic that this structure disappears at pressures higher than ~0.35 GPa, which was identified earlier as a tricritical point
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