Thermally induced magnetization switching in Fe/MnAs/GaAs(001): selectable magnetic configurations by temperature and field control

Abstract

Spintronic devices currently rely on magnetization control by external magnetic fields or spin-polarized currents. Developing temperature-driven magnetization control has potential for achieving enhanced device functionalities. Recently, there has been much interest in thermally induced magnetisation switching (TIMS), where the temperature control of intrinsic material properties drives a deterministic switching without applying external fields. TIMS, mainly investigated in rare-earth–transition-metal ferrimagnets, has also been observed in epitaxial Fe/MnAs/GaAs(001), where it stems from a completely different physical mechanism. In Fe/MnAs temperature actually modifies the surface dipolar fields associated with the MnAs magnetic microstructure. This in turn determines the effective magnetic field acting on the Fe overlayer. In this way one can reverse the Fe magnetization direction by performing thermal cycles at ambient temperatures. Here we use element selective magnetization measurements to demonstrate that various magnetic configurations of the Fe/MnAs/GaAs(001) system are stabilized predictably by acting on the thermal cycle parameters and on the presence of a bias field. We show in particular that the maximum temperature reached during the cycle affects the final magnetic configuration. Our findings show that applications are possible for fast magnetization switching, where local temperature changes are induced by laser excitations.

Dynamics of the MnAs α/β-Striped Microstructure and of the Fe Magnetization Reversal in Fe/MnAs/GaAs(001): An Optical-Laser Pump–Free-Electron-Laser Probe Scattering Experiment

“…At low temperatures (T < 10 °C), the Fe coercive field (58 Oe) is about twice that of α-MnAs (27 Oe), confirming that no (or very weak) coupling exists between the two ferromagnetic layers. For this specific sample, we also confirmed that MFe can be reversed by thermal cycling [13]. As mentioned above, by working in T-MOKE geometry one can improve considerably the magnetic asymmetry ratio with respect to employing circular polarization (Figure 1d).…”

“…Although a laser pulse is the external stimulus that promotes the magnetization reversal, here the underlying physics is rather different from the all-optical switching processes reported in the literature [15][16][17]. As for the static case [13], the laser-induced switching in Fe/MnAs is driven by the appearance and disappearance of surface dipolar fields, and its speed is determined by the timescales of the MnAs structural modifications in response to the external stimulus.…”

“…Later on, MnAs/GaAs(001) has been used as a template for growing a Fe ferromagnetic overlayer [10][11][12][13]. Taking advantage of the element selectivity of resonant x-ray magnetic scattering experiments, it was demonstrated that the direction of the Fe magnetization, M Fe , can be controlled by varying the morphology of the MnAs template via temperature driven stripe formation [11,13]. These results are interesting for potential applications in temperature induced magnetization switching, without applying external fields.…”

“…The sample, with the structure GaAs(001)/MnAs 200nm /Fe 3nm /ZnSe 4nm , was prepared at the Institut des NanoSciences de Paris, following the same molecular beam epitaxy procedure detailed before [10,13]. An atomically flat GaAs buffer layer was grown on the epi-ready GaAs(001) substrate, cleaned at~600 • C in As flux.…”

“…Soft x-ray resonant scattering studies of the morphological and magnetic properties of MnAs/GaAs [8,9] showed that the intensity of the stripe-related diffraction peaks observed in a rocking scan can serve as a benchmark for evaluating the average width of α and β stripes versus temperature [8]. Later on, MnAs/GaAs(001) has been used as a template for growing a Fe ferromagnetic overlayer [10][11][12][13]. Taking advantage of the element selectivity of resonant x-ray magnetic scattering experiments, it was demonstrated that the direction of the Fe magnetization, M Fe , can be controlled by varying the morphology of the MnAs template via temperature driven stripe formation [11,13].…”