The fundamental physical principles underlying the operation of basic spintronic elements were considered. The following effects were analyzed: giant magnetoresistance effect, injection of spin-polarized charge carriers from a magnetized ferromagnetic contact, radiative recombination in semiconductors involving spin-polarized carriers. An integrated GaAs-based structure implementing all of the above phenomena — a magnetoresistive spin light-emitting diode was fabricated and investigated. From the electrical circuit point of view, the device under consideration was a magnetoresistive element and a metal/tunnel-thin dielectric/semiconductor light-emitting diode connected in series. It was shown that a magnetic field directed in the plane of the layers changes the state of the magnetoresistive element (high or low resistance) and thus allows controlling the intensity of electroluminescence. The magnetic field directed perpendicular to the plane of the layers ensures magnetization of the magnetic contact of the light-emitting diode and spin injection, accompanied by the emission of circularly polarized light. As a result, a device formed possesses four stable magnetic states (high-low intensity, "positive"—"negative" circular polarization). Such a structure can serve as a basis for magnetic recording and information transmission elements, in which four stable states form quaternary logic instead of binary.