Simultaneous occurrence of Colossal Magnetocapacitance and Colossal Magnetoresistance

Mercury-chromium-sulfide, a material with relatively simple crystal structure (a "spinel") shows a complete alteration of its electronic characteristics if subjected to an external magnetic field. Already at relatively small fields, which may be produced even by commercial permanent magnets, the electrical resistance of the material drops significantly. In higher fields we observed a reduction up to a factor of one million, corresponding to the transformation from an insulator to a metal-like conductor.
Moreover, and even more exiting, in a magnetic field this material also shows a simultaneous, more than hundredfold increase of its dielectric constant. This quantity is vital for the construction of capacitors, which are among the most common electronic components. Such a strong coupling of electrical and magnetic properties has an immense potential for applications in modern microelectronics, e.g., for new faster and smaller memory devices. From a theoretical point of view, these unusual material properties are completely unexpected and probably are triggered by some quite exotic mechanism.

epsilon and rho

Temperature dependence of dielectric constant and dc resistivity for zero field and in an external magnetic field of 5 T. The insets provide a measure of the magneto-capacitive effect, with Δε' = ε'(5T) - ε'(0T), and the relative change of the resistivity with Δρ = ρ(0T) - ρ(5T).

S. Weber, P. Lunkenheimer, R. Fichtl, J. Hemberger, V. Tsurkan, and A. Loidl, Colossal Magnetocapacitance and Colossal Magnetoresistance in HgCr2S4, Phys. Rev. Lett. 96, 157202 (2006).