Magnetic and thermodynamic properties of the spin-dimer system La2RuO5 induced by Mn substitution

S. Riegg, A. Wintermeier, H.-A. Krug von Nidda, S. Widmann, A. Günther, A. Reller, S. G. Ebbinghaus, and A. Loidl
Phys. Rev. B 90, 024407 – Published 14 July 2014

Abstract

Magnetic properties as well as the specific heat of the spin-dimer system La2Ru1yMnyO5 were investigated for manganese concentrations 0y0.25. The magnetic (dc) susceptibility of the unsubstituted (y=0) system shows a steplike decrease close to 160 K reflecting a magnetostructural transition into a dimerized ground state. With increasing manganese concentration this behavior (typical for singlet formation) becomes continuously suppressed and the susceptibility bears the signatures of the emergence of new magnetic ground states. The high-temperature Curie-Weiss susceptibility can be described by Ru4+ (S=1) and Mn4+ (S=32) spin moments, with a dramatic decrease of the Curie-Weiss temperatures by almost 30% close to y=0.1, indicating significant changes in the average mean magnetic exchange. Field-cooled and zero-field-cooled experiments as well as ac-susceptibility measurements provide clear evidence for the formation of a spin-glass state, well below the characteristic dimerization temperature. The relaxation dynamics can be described by a Vogel-Fulcher-Tammann behavior and indicates high fragility when characterized in terms of glassy dynamics of canonical supercooled liquids. Additional electron-spin resonance experiments indicate different spin-glass regimes and a rather dynamic nature of the dimerized phase. In the Mn-substituted compounds, a linear contribution to the heat capacity at low temperatures can be ascribed to the spin-glass formation. With increasing manganese concentration, the anomaly in the specific heat caused by the spin-singlet formation is shifted to lower temperatures and becomes continuously suppressed and smeared out. On the basis of these results, we propose a (y,T)-phase diagram indicating the competition of the spin-glass and the dimerized states. We stress the similarities with doped CuGeO3, the canonical inorganic spin-Peierls system.

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  • Received 4 February 2014
  • Revised 13 June 2014

DOI:https://doi.org/10.1103/PhysRevB.90.024407

©2014 American Physical Society

Authors & Affiliations

S. Riegg1,*, A. Wintermeier1, H.-A. Krug von Nidda1, S. Widmann1, A. Günther1, A. Reller2, S. G. Ebbinghaus3, and A. Loidl1

  • 1Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, D-86159 Augsburg, Germany
  • 2Resource Strategy, University of Augsburg, D-86159 Augsburg, Germany
  • 3Solid State Chemistry, Martin-Luther-University Halle-Wittenberg, D-06099 Halle, Germany

  • *stefan.riegg@physik.uni-augsburg.de

See Also

Synthesis, crystal structure, and valence states of Mn-substituted La2RuO5

S. Riegg, F. J. Garcia-Garcia, A. Reller, A. Loidl, and S. G. Ebbinghaus
Phys. Rev. B 90, 024406 (2014)

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Vol. 90, Iss. 2 — 1 July 2014

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