Evolution of magnetic states in frustrated diamond lattice antiferromagnetic Co(Al1xCox)2O4 spinels

O. Zaharko, A. Cervellino, V. Tsurkan, N. B. Christensen, and A. Loidl
Phys. Rev. B 81, 064416 – Published 17 February 2010

Abstract

Using neutron powder diffraction and Monte Carlo simulations we show that a spin-liquid regime emerges at all compositions in the diamond-lattice antiferromagnets Co(Al1xCox)2O4. This spin-liquid regime induced by frustration due to the second-neighbor exchange coupling J2 is gradually superseded by antiferromagnetic collinear long-range order (k=0) at low temperatures. Upon substitution of Al3+ by Co3+ in the octahedral B site the temperature range occupied by the spin-liquid regime narrows and TN increases. To explain the experimental observations we considered magnetic anisotropy D or third-neighbor exchange coupling J3 as degeneracy-breaking perturbations. We conclude that Co(Al1xCox)2O4 is below the theoretical critical point J2/J1=1/8, and that magnetic anisotropy assists in selecting a collinear long-range ordered ground state, which becomes more stable with increasing x due to a higher efficiency of O-Co3+-O as an interaction path compared to O-Al3+-O.

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  • Received 21 January 2010

DOI:https://doi.org/10.1103/PhysRevB.81.064416

©2010 American Physical Society

Authors & Affiliations

O. Zaharko1,*, A. Cervellino1,2, V. Tsurkan3,4, N. B. Christensen1,5,6, and A. Loidl3

  • 1Laboratory for Neutron Scattering, ETHZ & PSI, CH-5232 Villigen, Switzerland
  • 2Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
  • 3Experimental Physics V, Center for Electronics Correlations and Magnetism, University of Augsburg, D-86159 Augsburg, Germany
  • 4Institute of Applied Physics, Academy of Sciences of Moldova, MD-2028 Chisinau, Republic of Moldova
  • 5Materials Research Division, Risø DTU, Technical University of Denmark, DK-4000 Roskilde, Denmark
  • 6Nano-Science Center, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark

  • *oksana.zaharko@psi.ch

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Vol. 81, Iss. 6 — 1 February 2010

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