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Ordered spin-ice state in the geometrically frustrated metallic ferromagnet Sm2Mo2O7

Surjeet Singh, R. Suryanarayanan, R. Tackett, G. Lawes, A. K. Sood, P. Berthet, and A. Revcolevschi
Phys. Rev. B 77, 020406(R) – Published 18 January 2008
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    Abstract

    The recent discovery of spin ice is a spectacular example of the noncoplanar spin arrangements that can arise in the pyrochlore A2B2O7 structure. We present magnetic and thermodynamic studies on the metallic ferromagnet pyrochlore Sm2Mo2O7. Our studies, carried out on oriented crystals, suggest that the Sm spins have an ordered spin-ice ground state below about T*=15K. The temperature and field evolution of the ordered spin-ice state are governed by an antiferromagnetic coupling between the Sm and Mo spins. We propose that as a consequence of a robust feature of this coupling, the tetrahedra aligned with the external field adopt a one-in, three-out spin structure as opposed to the three-in, one-out structure in dipolar spin ices, as the field exceeds a critical value.

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    • Received 6 November 2007

    DOI:https://doi.org/10.1103/PhysRevB.77.020406

    ©2008 American Physical Society

    Authors & Affiliations

    Surjeet Singh1, R. Suryanarayanan1, R. Tackett2, G. Lawes2, A. K. Sood3, P. Berthet1, and A. Revcolevschi1

    • 1Université Paris Sud, Laboratoire de Physico-Chimie de l’Etat Solide, UMR8182, , Bâtiment 414, Orsay, France
    • 2Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48202, USA
    • 3Department of Physics, Indian Institute of Science, Bangalore 560012, India

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    Issue

    Vol. 77, Iss. 2 — 1 January 2008

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    • Figure 1
      Figure 1
      (Color online) Temperature and magnetic field (inset) dependence of magnetization under several applied fields along [111] in a Sm2Mo2O7 crystal.Reuse & Permissions
    • Figure 2
      Figure 2
      (Color online) Isothermal magnetization in a single crystal of Sm2Mo2O7 at T=2 and 25K. Applied field along (a) [100], (b) [110], and (c) [111] crystallographic directions. (d) The expanded view shows the magnetization along the three axes close to saturation. The inset in (d) shows the temperature dependence of magnetization under a 10kOe field applied along the [100] and [111] axes. (e) Schematics of the proposed mechanism for the spin-flip transition under a [111] field in Sm2Mo2O7. The spin configuration on the Sm tetrahedron changes from the two-in, two-out to the one-in, three-out state (via flipping of the spin at site labeled x) as the applied field (H) exceeds a critical value HC. The resultant magnetic moment per Mo (Sm) tetrahedron is indicated by the thick arrow at the center of each tetrahedron.Reuse & Permissions
    • Figure 3
      Figure 3
      (Color online) Magnetic hysteresis loops in the [100] oriented crystal of Sm2Mo2O7 at several temperatures between 2 (outermost loop) and 75K. Inset shows a sharp increase in the coercive field, determined from the main figure panel, in the ordered spin-ice state below T*.Reuse & Permissions
    • Figure 4
      Figure 4
      (Color online) Specific heat (C), magnetic specific heat (Cmag), and change in magnetic entropy (ΔSmag) in Sm2Mo2O7.Reuse & Permissions
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