Large hysteretic magnetoresistance in high-mobility semiconductor quantum wires bridged by single-domain nanomagnets

Abstract

The authors discuss hysteresis in the magnetoresistance of hybrid semiconductor/ferromagnetic devices composed of high-mobility semiconductor quantum wires (QWs) bridged by single-domain Co nanomagnets (NMs). This hysteresis is shown to be consistent with the ballistic transport of electrons in the QW through the nonuniform magnetic field generated by the NM. It is also found to be strongly dependent on tilt angle, suggestive of a transition between easy- and hard-axis magnetizations.

Influence of quantum-interference on the fringing-field magnetoresistance of hybrid ferromagnetic/semiconductor devices

“…Although not shown, the MR peak in Fig. 1͑b͒ narrows as the sample is rotated away from the in-plane condition, 26 indicating it is indeed associated with the transverse component of the magnetic field, as expected for WL. This temperature scale correlates very well to that at which ⌬R / R min begins its decrease with reduction of temperature ͓Fig.…”

“…In this letter, we measure the MR of HFSDs over a wide range of temperature ͑T = 1.7-80 K͒. The structures are 2DEG-based quantum-wires bridged by nanomagnets, 26 which exhibit a clear hysteretic MR when their FMFs are modulated by an external field ͑B ext ͒. We find behavior in the magnitude of this hysteresis, in which, as we decrease temperature, we observe a crossover ͑at 5-10 K͒ from increasing to decreasing MR amplitude.…”

“…26 Results are presented for three devices, two of which had a single Co gate ͑devices 1 and 2 of Ref. 2͒, while the third was a three-gate device ͓Fig.…”

“…Here, we focus on the temperature dependence of the MR due to a pure magnetic barrier ͑i.e., the nanomagnets are grounded͒. The shape anisotropy of the nanomagnets favors magnetization along their length, 26 so to generate FMFs in the channel we applied an in-plane ͑within 1°͒ magnetic field a͒ Electronic mail: jbird@buffalo.edu. along the direction of current flow.…”

Electronic properties of quantum dots formed by magnetic double barriers in quantum wires

“…This is somewhat surprising, in particular considering that the necessary technology is essentially established. Several experiments on magnetic double barriers with submicron spacing have been performed in wide 2DEGs, 18,[28][29][30] with the minimum 2DEG width of 1 μm, reported in Ref. 28, which is probably too broad for detecting quantized states.…”