5 research outputs found
Critical properties of the double exchange ferromagnet Nd0.4Pb0.4MnO3
Results of a study of dc-magnetization M(T, H), performed on a Nd0.6Pb0.4MnO3
single crystal in the temperature range around T_C (Curie temperature) which
embraces the critical region | epsilon | = |T -T_C |/T_C <= 0.05 are reported.
The magnetic data analyzed in the critical region using the Kouvel-Fisher
method give the values for the T_C =156.47 +/- 0.06 K and the critical
exponents, beta = 0.374 +/- 0.006 (from the temperature dependence of
magnetization), and gamma = 1.329 +/- 0.003 (from the temperature dependence of
initial susceptibility). The critical isotherm M(T_C, H) gives delta = 4.547
+/- 0.1. Thus the scaling law gamma+beta=delta beta is fulfilled. The critical
exponents obey the single scaling-equation of state M(H, epsilon) = epsilon^b
f_+/- (H/epsilon^(beta + gamma)) where, f_+ for T > T_C and f_- for T< T_C. The
exponent values are very close to those expected for the universality class of
3D Heisenberg ferromagnets with short-range interactions.Comment: 19 pages, including 6 figure
Spectroscopic evidence of Kondo-induced quasi-quartet in CeRhAs
CeRhAs is a new multiphase superconductor with strong suggestions for
an additional itinerant multipolar ordered phase. The modeling of the low
temperature properties of this heavy fermion compound requires a quartet
Ce crystal-field ground state. Here we provide the evidence for the
formation of such a quartet state using x-ray spectroscopy. Core-level
photoelectron and x-ray absorption spectroscopy confirm the presence of Kondo
hybridization in CeRhAs. The temperature dependence of the linear
dichroism unambiguously reveils the impact of Kondo physics for coupling the
Kramer's doublets into an effective quasi-quartet. Non-resonant inelastic x-ray
scattering data find that the state with its lobes along
the 110 direction of the tetragonal structure ( orientation) contributes
most to the multi-orbital ground state of CeRhAs.Comment: 8 pages, 7 figure
Atomically resolved scanning tunneling microscopy on perovskite manganite single crystals
Atomically resolved scanning tunneling microscopy was conducted on cleaved single crystals of the cubic perovskite Pr0.68Pb0.32MnO3.Several different surface configurations could be resolved including a frequent square arrangement with atomic distances in excellent agreement to the bulk lattice constant of the cubic structure. We also observed stripe formation and a surface reconstruction. The latter is likely related to a polar rare earth-oxygen terminated surface. (C) 2010 American Institute of Physics
Density of states and spatially inhomogeneous conductance near the metal-insulator transition in single crystals
Single crystals of Pb have been investigated by scanning tunneling microscopy over a broad temperature range. In this material, a distinct separation of the ferromagnetic and the metal–insulator transition temperature, TC210 K and TMI255 K, respectively, was observed. Spectroscopic tunneling studies revealed that even on a local scale the system switches from predominantly metallic to insulating within a narrow temperature range around Inhomogeneities of the zero-bias conductance with small patches of metallic clusters on a length scale of 2–3 nm, however, were only observed within the temperature range TC<T<TMI. The results give direct evidence for phase separation in the paramagnetic metallic state, but homogeneous ferromagnetic and insulating states
Interplay of structural distortions, dielectric effects and magnetic order in multiferroic GdMnO3
Multiferroic materials are characterized by simultaneous magnetic and ferroelectric ordering making them good candidates for magneto-electrical applications. We conducted thermal expansion and magnetostriction measurements in magnetic fields up to 14 T on perovskitic GdMnO3 by highresolution capacitive dilatometry in an effort to determine all longitudinal and transversal components of the magnetostriction tensor. Below the ordering temperature T (N) = 42 K, i.e., within the different complex (incommensurate or complex) antiferromagnetic phases, lattice distortions of up to 100 ppm have been found. Although no change of the lattice symmetry occurs, the measurements reveal strong magneto-structural phenomena, especially in the incommensurate sinusoidal antiferromagnetic phase. A strong anisotropy of the magnetoelastic properties was found, in good agreement with the type and propagation vector of the magnetic structure. We demonstrate that our capacitive dilatometry can detect lattice expansion effects and changes of the dielectric permittivity simultaneously because the sample is housed inside the capacitor. A separation of both effects is possible by shielding the sample. Dielectric transitions could be detected by this method and compared to the critical values of H and T in the magnetic phase diagram. Dielectric changes measured at 1 kHz excitation frequency are detected in GdMnO3 at about 180 K, and between 10 K and 25 K in the canted antiferromagnetic structure which is characterized by a complex magnetic order on both the Gd- and Mn-sites