Magnetocapacitance as a sensitive probe of magnetostructural changes in NiCr2O4

Taylor D. Sparks, Moureen C. Kemei, Phillip T. Barton, Ram Seshadri, Eun-Deok Mun, and Vivien S. Zapf
Phys. Rev. B 89, 024405 – Published 10 January 2014

Abstract

The spinel NiCr2O4 is characterized using dielectric and high-magnetic-field measurements. The trends in the magnetodielectric response fall into three clear temperature regimes corresponding to known magnetic and structural transitions. Above the Néel temperature, weak magnetic field dependence of the dielectric constant is observed with no hysteresis. Below the Néel temperature but above 30 K, a dependence of the dielectric constant on the magnetic field is observed and hysteresis develops, resulting in so-called butterfly loops. Below 30 K, magnetodielectric hysteresis is enhanced. Magnetodielectric hysteresis mirrors magnetic hysteresis, suggesting that spin-spin interactions are the mechanism for the magnetodielectric effect in NiCr2O4. We show that below 40 kOe, the field-dependent permittivity scales linearly with the squared magnetization as described by the Ginzburg-Landau theory. At high fields, however, the magnetization continues to increase while the dielectric constant saturates. Magnetodielectric measurements of NiCr2O4 suggest an additional, previously unobserved, transition at 20 K. Subtle changes in magnetism and structure at 20 K, suggest the completion of ferrimagnetic ordering and the spin-driven structural distortion. We demonstrate that magnetocapacitance is a sensitive probe of magnetostructural distortion and provide the first high-field measurements of NiCr2O4.

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  • Received 30 August 2013
  • Revised 26 November 2013

DOI:https://doi.org/10.1103/PhysRevB.89.024405

©2014 American Physical Society

Authors & Affiliations

Taylor D. Sparks*, Moureen C. Kemei, Phillip T. Barton, and Ram Seshadri§

  • Materials Department and Materials Research Laboratory, University of California, Santa Barbara, California 93106, USA

Eun-Deok Mun and Vivien S. Zapf

  • National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

  • *Current address: Materials Science and Engineering Department University of Utah, Salt Lake City, UT 84112; sparks@eng.utah.edu.
  • kemei@mrl.ucsb.edu
  • pbarton@mrl.ucsb.edu
  • §seshadri@mrl.ucsb.edu
  • edmun@lanl.gov
  • vzapf@lanl.gov

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Vol. 89, Iss. 2 — 1 January 2014

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