Spin correlations and colossal magnetoresistance in HgCr${}_2$Se${}_4$

Abstract

This study aims to unravel the mechanism of colossal magnetoresistance (CMR) observed in n-type HgCr${}_2$Se${}_4$, in which low-density conduction electrons are exchange-coupled to a three-dimensional Heisenberg ferromagnet with a Curie temperature $T_C\approx$ 105 K. Near room temperature the electron transport exhibits an ordinary semiconducting behavior. As temperature drops below $T^{\ast }\simeq 2.1T_C$, the magnetic susceptibility deviates from the Curie-Weiss law, and concomitantly the transport enters an intermediate regime exhibiting a pronounced CMR effect before a transition to metallic conduction occurs at $T<T_C$. Our results suggest an important role of spin correlations not only near the critical point, but also for a wide range of temperatures ($T_C<T<T^{\ast }$) in the paramagnetic phase. In this intermediate temperature regime the transport undergoes a percolation type of transition from isolated magnetic polarons to a continuous network when temperature is lowered or magnetic field becomes stronger.

arXiv comment12 pages, 5 figures in main text and 8 figures in appendices

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• Unconventional temperature dependence of the anomalous Hall effect in HgCr2Se4
• Magnetic competition induced colossal magnetoresistance in n-type HgCr2Se4 under high pressures
• Linear colossal magnetoresistance driven by magnetic textures in LaTiO3 thin films on SrTiO3