We report on the magnetotransport properties of epitaxial thin films of In 1−x Mn x Sb dilute magnetic semiconductor grown by metal-organic vapor-phase epitaxy. At temperatures below 10 K, a negative magnetoresistance dominates the magnetotransport that is attributed to spin-dependent scattering by localized magnetic moments. Above 10 K, the magnetoresistance is positive and is well described by a two-band model consisting of spin-split hybridized p-d subbands with different conductivities. Hall effect measurements show an anomalous behavior that persists up to room temperature, providing an indication of ferromagnetic order. In addition, magnetization measurements reveal distinct hysteresis loops at room temperature which confirms the ferromagnetism of the films.
The giant magnetoresistance characteristics of magnetic III-V semiconductor p-n heterojunctions are described. The origin of the extremely large positive magnetoresistance ͑2680%͒ observed at room temperature and at a field of 18 T is attributed to efficient spin-polarized carrier transport. The magnetocurrent ratio of the junction saturates with magnetic field. The field dependence of the magnetoresistance points to the existence of a paramagnetic component, which determines the degree of spin polarization of the junction current. This work indicates that highly spin-polarized magnetic semiconductor heterojunction devices that operate at room temperature can be realized.
We report ferromagnetism in single phase, epitaxial In 1−x Mn x Sb alloy films, with x Յ 0.035, grown by metalorganic vapor phase epitaxy. The alloy films exhibit well-defined magnetization versus magnetic field hysteresis loops from 4-298 K. High-field magnetotransport measurements indicated that the Hall resistivity has a nonlinear dependence on magnetic field. Ferromagnetism is supported by observation of an anomalous Hall effect and clear hysteresis in the anomalous Hall resistivity versus magnetic field measurements. Zero field cooled and field cooled magnetization measurements show reversibility indicating absence of second phase precipitates. The temperature dependence of the magnetization is described by a modified Brillouin function with a T C of 590 K. The observed magnetic and magnetotransport properties are attributed to carrier mediated ferromagnetism involving Mn and its complexes that form shallow or resonant electronic states through correlated substitution in the semiconductor host.
We have demonstrated the first bipolar magnetic junction transistor using a dilute magnetic semiconductor. For an InMnAs p-n-p transistor magnetoamplification is observed at room temperature. The observed magnetoamplification is attributed to the magnetoresistance of the magnetic semiconductor InMnAs heterojunction. The magnetic field dependence of the transistor characteristics confirm that the magnetoamplification results from the junction magnetoresistance. To describe the experimentally observed transistor characteristics, we propose a modified Ebers-Moll model that includes a series magnetoresistance attributed to spin-selective conduction. The capability of magnetic field control of the amplification in an all-semiconductor transistor at room temperature potentially enables the creation of new computer logic architecture where the spin of the carriers is utilized.
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