Colossal magnetoresistance

About: Colossal magnetoresistance is a research topic. Over the lifetime, 3658 publications have been published within this topic receiving 130104 citations.

GMR enhancement in inhomogeneous semiconductors for use in magnetoresistance sensors

Abstract: The low-field magnetoresistance of a high carrier mobility semiconductor with inhomogeneities which are more conducting than the surrounding semiconductor material matrix is significantly enhanced compared to the magnetoresistance of the homogeneous material. The enhancement results from a magnetic field induced geometric effect in which current is expelled from the conducting inhomogeneity. The enhanced giant magnetoresistance is demonstrated at low field in (near) zero-band-gap material, such as Hg 1-x Cd x Te(x˜0.1). The effect is applied to the fabrication of magnetic read head sensors such as Corbino disc, bar magnetoresistance sensors and thin film sensors.

Phase Transitions at the Nanoscale in Functional Materials

Abstract: Many properties of functional materials are quite different at the nanoscale, because at this length scale, the surface/interface energy becomes comparable to the bulk energy. Thus, the nature of various phase transitions at the nanoscale (e.g., structural, electronic, magnetic, metal-insulator) is altered. In addition, in functional materials with many coupled order parameters, quantum effects can dominate the response. We use the term nanoscale with three different context-specific connotations: it could refer to a cluster of atoms or molecules, a confined geometry as in a nanoscale grain or a superlattice, and a nanoscale region in the bulk. This field is still in its infancy, and much needs to be learned in terms of nucleation and thermodynamics at this scale. Materials of interest that we consider in this issue include, but are not limited to, ferroics (ferroelectrics, ferromagnets, ferroelastics), multiferroics (magnetoelectrics, ferrotoroidics), and complex functional materials such as those that exhibit colossal magnetoresistance and high-temperature superconductivity, including the recently discovered iron pnictide superconductors. Superconductors provide a fertile ground for quantum phase transitions.

Colossal Terahertz Magnetoresistance at Room Temperature in Epitaxial La0.7Sr0.3MnO3 Nanocomposites and Single-Phase Thin Films

Abstract: Colossal magnetoresistance (CMR) is demonstrated at terahertz (THz) frequencies by using terahertz time-domain magnetospectroscopy to examine vertically aligned nanocomposites (VANs) and planar thin films of La0.7Sr0.3MnO3. At the Curie temperature (room temperature), the THz conductivity of the VAN was dramatically enhanced by over 2 orders of magnitude under the application of a magnetic field with a non-Drude THz conductivity that increased with frequency. The direct current (dc) CMR of the VAN is controlled by extrinsic magnetotransport mechanisms such as spin-polarized tunneling between nanograins. In contrast, we find that THz CMR is dominated by intrinsic, intragrain transport: the mean free path was smaller than the nanocolumn size, and the planar thin-film exhibited similar THz CMR to the VAN. Surprisingly, the observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for alternating current motion on nanometer length scales, even when the magnetoresistance is negli...

Mutual influence between current-induced giant magnetoresistance and radiation-induced magnetoresistance oscillations in the GaAs/AlGaAs 2DES.

Abstract: Radiation-induced magnetoresistance oscillations are examined in the GaAs/AlGaAs 2D system in the regime where an observed concurrent giant magnetoresistance is systematically varied with a supplementary dc-current, I dc . The I dc tuned giant magnetoresistance is subsequently separated from the photo-excited oscillatory resistance using a multi-conduction model in order to examine the interplay between the two effects. The results show that the invoked multiconduction model describes the observed giant magnetoresistance effect even in the presence of radiation-induced magnetoresistance oscillations, the magnetoresistance oscillations do not modify the giant magnetoresistance, and the magnetoresistance oscillatory extrema, i.e., maxima and minima, disappear rather asymmetrically with increasing I dc . The results suggest the interpretation that the I dc serves to suppress scattering between states near the Fermi level in a strong magnetic field limit.