Magnetocapacitance as a sensitive probe of magnetostructural changes in NiCr2O4

作者：Sparks Taylor D^*; Kemei Moureen C; Barton Phillip T; Seshadri Ram; Mun Eun Deok; Zapf Vivien S

来源：Physical Review B, 2014, 89(2): 024405.

DOI：10.1103/PhysRevB.89.024405

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 Neel temperature, weak magnetic field dependence of the dielectric constant is observed with no hysteresis. Below the Neel 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.

• 出版日期2014-1-10