Colossal Magnetoresistance in Magnetically Doped Quantum Wells

1. Colossal Magnetoresistance in Magnetically Doped Quantum Wells J. Jaroszyńskia, T. Andrearczykb, G. Karczewskib, J. Wróbelb, T. Wojtowiczb, D. Popovića, and T. Dietlb a) National High Magnetic Field Laboratory, FSU, Tallahassee, FL b) Institute of Physics, Polish Academy of Sciences, Warsaw, PL Supported by NSF DMR-0403491 (PI: Dragana Popović) andNHMFL via NSF Cooperative Agreement DMR-0084173 We fabricated a novel magnetic semiconductor device with electric gate. The gate controls not only electron density, like in widely used silicon field transistors, but also magnetic properties. It is easy to switch between different magnetic phases just by applying a small voltage. This regulation possibility is very attractive for spintronics, an emerging technology that uses not only electric but also magnetic properties for data processing. Interestingly, magnetoresistance (MR) studies in these (Cd,Mn)Te quantum wells reveal a new glassy phase near the metal-insulator transition. Moreover, in this phase a dramatic increase of the zero-field resistance and strong negative MR resemble features commonly observed in colossal magnetoresistive materials (e.g. manganites). The phase diagram of the system shows further similarities to transitional oxides with a characteristic “dome” of anomalous behavior at the boundary of metallic and insulating phases. The phase diagram of anomalous transport behavior, also shows possible magnetic phases (FM-ferromagnetic, AF antiferromagnetic, PM-paramagnetic). Jaroszyński, J.; Andrearczyk, T.; Karczewski, G.; Wróbel, J.; Wojtowicz, T.; Popović, D. and Dietl, T., “Intermediate phase at the metal-insulator boundary in a magnetically doped two-dimensional electron system”, Phys. Rev. B, 76, 045322 (2007)