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Title: Decoupling of the antiferromagnetic and insulating states in Tb-doped Sr2IrO4

Sr2IrO4 is a spin-orbit coupled insulator with an antiferromagnetic (AFM) transition at TN = 240 K. We report results of a comprehensive study of single-crystal Sr2Ir1-xTbxO4 (0≤x≤0.03). This study found that mere 3% (x=0.03) tetravalent Tb4+(4f7) substituting for Ir4+ (rather than Sr2+) completely suppresses the long-range collinear AFM transition but retains the insulating state, leading to a phase diagram featuring a decoupling of magnetic interactions and charge gap. The insulating state at x = 0.03 is characterized by an unusually large specific heat at low temperatures and an incommensurate magnetic state having magnetic peaks at (0.95, 0, 0) and (0, 0.95, 0) in the neutron diffraction, suggesting a spiral or spin density wave order. It is apparent that Tb doping effectively changes the relative strength of the SOI and the tetragonal CEF and enhances the Hund’s rule coupling that competes with the SOI, and destabilizes the AFM state. However, the disappearance of the AFM accompanies no metallic state chiefly because an energy level mismatch for the Ir and Tb sites weakens charge carrier hopping and renders a persistent insulating state. Furthermore, this work highlights an unconventional correlation between the AFM and insulating states in which the magnetic transition plays nomore » critical role in the formation of the charge gap in the iridate.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [4] ;  [5] ;  [4] ;  [6] ;  [7] ;  [2] ;  [2]
  1. Univ. of Kentucky, Lexington, KY (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Renmin Univ. of China, Beijing (China)
  2. Univ. of Kentucky, Lexington, KY (United States)
  3. Univ. of Kentucky, Lexington, KY (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
  5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  6. Florida State Univ., Tallahassee, FL (United States)
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1248025
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 92; Journal Issue: 21; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society (APS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY