Magnetoresistance oscillations induced by periodically arranged micromagnets (invited)

Abstract

Probing magnetic fields can be done, e.g., by employing the well established Hall effect. Alternatively, we make use of the ballistic motion of electrons in high mobility two-dimensional electron systems ͑2DES͒ to probe electrically the stray field of periodically arranged micomagnets. We investigate the magnetoresistance of the 2DES underneath arrays of magnetic strips and magnetic dots having periods between 500 nm and 1 m. The periodic stray field gives rise to pronounced oscillations of the resistivity as a function of a homogeneous ͑weak͒ magnetic field. The magnetization orientation of the dots and strips can be aligned in different directions with respect to the current flow through the device. The observed magnetoresistance depends characteristically on the magnetization direction and can be understood in terms of the stray field pattern probed by the electrons.

Morphological and magnetic characteristics of monodispersed Co-cluster assemblies

“…Apart from these metallurgical and conventional methods, by which the concentration and morphology cannot be independently controlled, laser or electron beam micro/nanolithography techniques permit the fabrication of submicrometer-scale magnetic dots, wires and arrays. 8,9 However, the lowest fabricated size obtained using lithography is about 20 nm. Submicrometer-to nanometersized fine particles have also been produced by inert gas condensation and colloidal methods, 10 and intensively studied for magnetic recording media and micromagnetic devices, although it is difficult to obtain monodispersed particles less than 10 nm by these methods.…”

2D Electron Gas in Non-Uniform Magnetic Fields

“…Figure 9 shows measured Rxx plotted against z-component of the external magnetic field, Bextz , for Bext perpendicular to the plane of the 2DEG (g5 = 0°) and at 4 = 80° (note the logarithmic scale). The strong low field magnetoresistance oscillations are not Shubnikov-de Haas oscillations but result from commensurability between the diameter of the cyclotron orbit at the Fermi level and the period of the magnetic modulation [7][8][9][10][11][12][13][14]. These commensurability oscillations are closely related to those seen for electrostatic modulation [7,8].…”

“…The transport properties of two-dimensional electron systems in 1D and 2D periodically modulated magnetic fields have been studied extensively [7][8][9][10][11][12][13][14]. The type of device used is illustrated schematically in Fig.…”

“…The more direct approach, which several groups [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] have pursued, is the fabrication of lithographically patterned ferromagnetic structures above near--surface 2DEGs. Micron or submicron ferromagnetic elements such as magnetic dots and stripes can be used to produce a range of field profiles at the 2DEG.…”

Transport of spin-polarized electrons in a magnetic superlattice

“…Similarly, the forth and fifth terms are Dresselhaus terms with the Dresselhaus coupling coefficient ␤͑x͒. In constructing the model, the possible straininduced electrostatic potentials modulation 18 has been neglected.…”