Annealed Local Magnetic Moments and the Metal-Insulator Transition in Disordered Electronic Systems

2002 ◽  
Vol 230 (1) ◽  
pp. 97-100
Author(s):  
T. Vojta ◽  
D. Belitz ◽  
T.R. Kirkpatrick
Keyword(s):  
Magnetic Moments ◽  
Insulator Transition ◽  
Electronic Systems ◽  
Metal Insulator Transition ◽  
Metal Insulator

scholarly journals Magnetic structure and 5d-electronic state in a pyrochlore iridate Eu2Ir2O7

2014 ◽  
Vol 70 (a1) ◽  
pp. C1457-C1457
Author(s):  
Hajime Sagayama ◽  
Daisuke Uematsu ◽  
Taka-hisa Arima ◽  
Jun Ishikawa ◽  
Eoin O'Farrell ◽  
...  
Keyword(s):  
Electronic State ◽  
Magnetic Moments ◽  
Crystal Structure Analysis ◽  
Insulator Transition ◽  
Face Centered Cubic ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

The pyrochlore-type iridium oxide Eu2Ir2O7 exhibits a metal-insulator transition at 120 K, accompanied by magnetic ordering. We performed resonant x-ray scattering (RXS) experiment with photon energies near the iridium absorption edge L3 to investigate the arrangement of Ir4+ magnetic moments. Magnetic RXS was observed in the insulating phase, providing direct evidence of long-range ordering of Ir4+ magnetic moments with a propagation vector of (4n+2 0 0) . Our single-crystal structure analysis revealed that the lattice retains its face-centered-cubic structure across the metal-insulator transition, indicating all-in-all-out magnetic order, where all the magnetic moments on the four vertices of each Ir4+ tetrahedron point inward or outward as shown in Fig. 1 [1]. To investigate the 5d-electronic state of Ir4+, we performed resonant inelastic x-ray scattering (RIXS) experiment near the L3 edge. Obtained RIXS spectra indicate that the 5d-electronic state is affected by not only the spin-orbit interaction but also trigonal distortion of IrO6 octahedron [2].

1/f NOISE NEAR THE METAL-INSULATOR TRANSITION

1994 ◽  
Vol 08 (07) ◽  
pp. 897-903 ◽  
Author(s):  
Oded Cohen ◽  
Zvi Ovadyahu
Keyword(s):  
Noise Level ◽  
Flicker Noise ◽  
Insulator Transition ◽  
Electronic Systems ◽  
Metal Insulator Transition ◽  
Static Disorder ◽  
Metal Insulator ◽  
Anderson Transition ◽  
Conductance Fluctuations ◽  
Insulating Phase

The 1/f noise level in polycrystalline indium oxide thin films and of zinc oxide accumulation layers is found to be much higher than that usually observed in metals. A systematic study of the flicker noise properties in these systems reveals a correlation between the 1/f noise magnitude and the proximity of the system to the insulating phase. In fact, the noise appears to increase dramatically close to the Anderson transition but when the average transport properties exhibited by the system are still diffusive. For static disorder that exceeds the critical value characterized by KFl≃1 the system exhibits insulating behavior and the noise level saturates at a rather high, but disorder independent value. The similarity of these findings to the behavior of the magnetic-field-induced Conductance Fluctuations in this system will be pointed out to suggest a common physical origin. This leads to the prediction of high levels of 1/f in all electronic systems that are close to the metal-insulator transition.

scholarly journals LOCAL PSEUDOGAPS AND FREE MAGNETIC MOMENTS AT THE ANDERSON METAL-INSULATOR TRANSITION: NUMERICAL SIMULATION USING POWER-LAW BAND RANDOM MATRICES

2012 ◽  
Vol 11 ◽  
pp. 102-107
Author(s):  
IMRE VARGA ◽  
STEFAN KETTEMANN ◽  
EDUARDO R. MUCCIOLO
Keyword(s):  
Power Law ◽  
Local Density ◽  
Magnetic Moments ◽  
Insulator Transition ◽  
Local Density Of States ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Anderson Transition ◽  
Continuous Parameter ◽  
Unitary Ensemble

At the Anderson metal-insulator transition the eigenstates develop multifractal fluctuations. Therefore their properties are intermediate between being extended and localized. As a result these wave functions are power-law correlated, which causes a substantial suppression of the local density of states at some random positions, resembling random local pseudogaps at the Fermi energy. Consequently the Kondo screening of magnetic moments is suppressed when a magnetic impurity happens to be at such a position. Due to these unscreened magnetic moments the critical exponents and multifractal dimensions at the metal-insulator transition take their smaller, unitary ensemble values for exchange couplings not exceeding a certain critical value J* ≈ .3D, where D is the band width. Here we present numerical calculations of the distribution of Kondo temperatures for the critical Power-law Band Random Matrix (PBRM) ensemble, whose properties are similar to that of the Anderson transition with the advantage of using a continuous parameter for tuning the generalized multifractal dimensions of the eigenstates.

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