Low voltage control of exchange coupling in a ferromagnet-semiconductor quantum well hybrid structure

Abstract

Voltage control of ferromagnetism on the nanometer scale is highly appealing for the development of novel electronic devices with low power consumption, high operation speed, reliable reversibility and compatibility with semiconductor technology. Hybrid structures based on the assembly of ferromagnetic and semiconducting building blocks are expected to show magnetic order as a ferromagnet and to be electrically tunable as a semiconductor. Here, we demonstrate the electrical control of the exchange coupling in a hybrid consisting of a ferromagnetic Co layer and a semiconductor CdTe quantum well, separated by a thin non-magnetic (Cd,Mg)Te barrier. The electric field controls the phononic ac Stark effect—the indirect exchange mechanism that is mediated by elliptically polarized phonons emitted from the ferromagnet. The effective magnetic field of the exchange interaction reaches up to 2.5 Tesla and can be turned on and off by application of 1V bias across the heterostructure.

Half-Metal–Spin-Gapless-Semiconductor Junctions as a Route to the Ideal Diode

“…As mentioned above, although at zero bias the coupling between the SGS and HMM electrodes is ferromagnetic, we find that this coupling changes sign from ferromagnetic to antiferromagnetic under a forward bias of about 180 mV. Note that electric field or voltage control of magnetism on the nanoscale is highly appealing for the development of nanoelectronic devices with low power consumption [62][63][64]. A voltage-induced interlayer exchange coupling in magnetic tunnel junctions has been discussed theoretically via high-voltage tunneling [65][66][67] and has been experimentally demonstrated via mobile oxygen vacancies [68].…”

Optically Induced Spin Electromotive Force in a Ferromagnetic–Semiconductor Quantum Well Structure

“…A long-range interaction between the spins of QW holes and FM magnetic atoms has been found in hybrid structures based on a Co,Fe/CdTe QW. 1,2 A nontrivial phenomenon of carrier spin polarization was also found in the GaAs/InGaAs system with a GaMnAs FM layer adjacent to the InGaAs QW. In the absence of optical excitation, the spin polarization of the majority of charge carriers (holes) in the QW was detected electrically 3 and was explained by the short-range exchange interaction of holes in the QW with the FM.…”

“…8,9 In our case QW embedded into the structure near the interface sets the nanometer scale depth resolution of proximity magnetic effect, provided that the QW is excited resonantly. 2 For hybrid structures with a few-nanometer-thick barrier, PL signal under resonant excitation is too weak due to the strong non-radiative recombination of the photoexcited carriers, which tunnel from the QW into the FM. On the contrary, the spin-photo-voltage signal in such case is reliably measured and thus appears to be a working tool to study the magnetic proximity effect on a nanometer spatial scale, where it is inaccessible for resonant-PL technique.…”

2D electron gas in chalcogenide multilayers

“…Application of electric field across such a ferromagnet-semiconductor hybrid structure changes the splitting of the heavy-hole and light-hole states thus affecting phonon coupling. It was shown [95] that electric field strengths of the order of 10 4 V /cm are sufficient to bring heavy-to-light hole transition out of resonance with the magnon-phonon resonance of the ferromagnet. Therefore, low voltage electric control of the conceptually new long-range exchange coupling mediated by elliptically polarized phonons is possible.…”