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Switching of magnetization by spin–orbit torque in the (Ga,Mn)(As,P) film was studied with currents along ⟨100⟩ crystal directions and an in-plane magnetic field bias. This geometry allowed us to identify the presence of two independent spin–orbit-induced magnetic fields: the Rashba field and the Dresselhaus field. Specifically, we observe that when the in-plane bias field is along the current (I ∥ Hbias), switching is dominated by the Rashba field, while the Dresselhaus field dominates magnetization reversal when the bias field is perpendicular to the current (I ⊥ Hbias). In our experiments, the magnitudes of the Rashba and Dresselhaus fields were determined to be 2.0 and 7.5 Oe, respectively, at a current density of 8.0 × 105 A/cm2. [ABSTRACT FROM AUTHOR]

We have investigated the exchange bias (EB) effect occurring in (Ga, Mn)As/(Ga, Mn)(As, P) bilayers, in which the (Ga, Mn)As layer has an in-plane (IP) magnetic anisotropy, and the magnetic anisotropy of the (Ga, Mn)(As, P) layer is out-of-plane (OP). Planar Hall resistance (PHR) measured during magnetization reversal in this system showed a clear shift of the hysteresis loops, indicating the presence of EB in the (Ga, Mn)As layer. The EB significantly depends on the direction of the field used in the field-cooling process. The observed EB occurring in a bilayer in which the constituent layers have orthogonal magnetic anisotropies can be understood in terms of the formation of magnetic closure domains in the (Ga, Mn)(As, P) layer during field cooling. We show that such EB can be effectively controlled by the process of field cooling, suggesting the possibility of memory device applications based on bilayer systems with orthogonal magnetic anisotropy. [ABSTRACT FROM AUTHOR]

Highlight • The planar Hall resistance measurements revealed two GaMnAs layers have opposite sign of AMR. • Alignment of magnetizations between GaMnAs have been identified form Hall measurements. • GaMnAs trilayer showed GMR-like effect that arises from the noncollinear configurations. Abstract The magnetotransport properties of a GaMnAs trilayer in which two GaMnAs layers are separated by a nonmagnetic GaAs:Be spacer has been investigated during the magnetization reversal process. Interestingly, the planar Hall resistance (PHR) reveals that the two GaMnAs layers in a trilayer structure have opposite signs of anisotropic magnetoresistance (AMR). The magnetoresistance is observed to be significantly different for the collinear and noncollinear magnetic alignment, which indicates that the presence of the giant magnetoresistance (GMR)-like effect in the system. This GMR-like effect was systematically investigated during the process of magnetization reversal using field and angle scans of MR measurements. [ABSTRACT FROM AUTHOR]

Spin–orbit-induced (SOI) field of crystalline GaMnAs ferromagnetic film has been investigated by using planar Hall effect measurements. The presence of SOI field manifested itself as an asymmetry in the magnetization reversal process between positive and negative current directions. A significant Joule heating caused by current has been observed and its effect was carefully considered to obtain the magnetic anisotropy of the GaMnAs film. The switching of magnetization by SOI field in the GaMnAs film was demonstrated in the absence of an external field. [ABSTRACT FROM AUTHOR]

Interlayer exchange coupling (IEC) between ferromagnetic (FM) metal Fe and FM semiconductor GaMnAs has been investigated by using magnetotransport measurements. The realization of diverse magnetization alignments, including collinear and non-collinear configurations, between Fe and GaMnAs layers are observed during the magnetization reversal process measured by the planar Hall effect. Minor loop scan reveals the presence of FM IEC between Fe and GaMnAs, which systematically decreases as the temperature increases. [ABSTRACT FROM AUTHOR]

We discuss tunneling magnetoresistance (TMR) phenomena observed in hybrid magnetic tunnel junctions (MTJs) fabricated from a Fe/GaAlAs/GaMnAs trilayer. The TMR clearly shows abrupt changes of resistance that depends on the relative alignments of magnetization in the two magnetic layers comprising the MTJ. The TMR ratio of the structure strongly depends on the bias voltage, reaching values up to ~45% when the bias voltage is low (~0.2mV). In addition, the device exhibits intermediate TMR values, which correspond to non-collinear alignments of magnetization in the GaMnAs and the Fe layers. Such alignments are possible due to the presence of two magnetic easy axes both in both magnetic layers originating from their strong cubic magnetic anisotropy. The TMR states realized in such Fe/GaAlAs/GaMnAs MTJs are excellent candidates for use in multi-valued memory storage devices. [ABSTRACT FROM AUTHOR]

We have investigated magnetic properties of Ni film specimens deposited either on GaAs or on Bi2Se3 surfaces. The magnetization saturation field along the out-of-plane direction observed in the Hall data was weaker for the Ni/Bi2Se3 sample than for the Ni/GaAs sample. On the other hand, planar Hall resistance measurements showed the larger in-plane coercive field for Ni/Bi2Se3 than for Ni/GaAs. These changes of magnetic hardness observed along the out-of-plane and in-plane directions in the Ni/Bi2Se3 specimen are consistent with effects arising from spin–orbit interaction at the surface of the Bi2Se3 topological insulator. [ABSTRACT FROM AUTHOR]

Interlayer exchange coupling (IEC) between GaMnAs layers in GaMnAs/InGaAs/GaMnAs tri-layers was studied by magnetization measurements. Minor hysteresis loops are observed to shift in a direction indicating the presence of ferromagnetic (FM) IEC in the structures. The strength of the FM IEC clearly exhibits an exponential decrease with respect to nonmagnetic InGaAs spacer thickness. The fitting of the spacer thickness dependence of the FM IEC to an exponential decay function provides a decay length of 3.3±0.3 nm, which is relatively large compared to metallic multilayers, indicating a long ranged IEC in systems based on GaMnAs. [ABSTRACT FROM AUTHOR]

We report a systematic investigation of ac magnetic susceptibility in (Ga,Mn)As films as a function of temperature and magnetic field, carried out in parallel with dc magnetization measurements. The temperature dependence of ac susceptibility \chi ac shows anisotropic behavior: 1) a single peak in \chi ac is observed close to TC for the [ 1\bar 10 ] orientation of the driving ac field; 2) a single peak is also seen close to 22 K for the field along [110]; and 3) peaks at both these temperatures are observed for the field applied along [100]. A detailed analysis of the ac and dc data unambiguously indicates that the peak near TC is related to the paramagnetic-to-ferromagnetic phase transition, with the ferromagnetic domains nucleating with their easy axes aligned with the [ 1\bar 10 ] direction, providing a clear picture of uniaxial domain behavior near TC . The peak near 22 K, on the other hand, is related to the onset of biaxial domain structure in (Ga,Mn)As induced by the competition between uniaxial and cubic anisotropy. More specifically, the ac susceptibility peak near TC involves 180° magnetization flips along the [ 1\bar 10 ] easy axis of the domains, while the peak near 22 K originates from magnetization wobbling between two biaxial easy axes separated by a small angle. [ABSTRACT FROM AUTHOR]

Interlayer exchange coupling (IEC) between the GaMnAs layers in GaMnAs/GaAs:Be multilayer systems has been investigated using magnetotransport experiments. The observation of a stable antiparallel magnetization alignment state from the systems indicates the presence of antiferromagnetic (AFM) IEC between the GaMnAs layers. The transitions between parallel and antiparallel alignments of GaMnAs magnetic layers in the system were carefully investigated by measuring resistance change with increasing temperature under various bias magnetic fields. From the dependence of the transition temperature on bias fields, we have estimated the magnitude of AFM IEC and its temperature behavior of our GaMnAs/GaAs:Be multilayers. [ABSTRACT FROM AUTHOR]

Ultrafast laser-triggered coherent magnetization dynamics in ferromagnetic (Ga,Mn)As films have been investigated by time-resolved magneto-optical spectroscopy. Dynamic phase reversal in the magnetic precession process is observed when the ambient temperature or the external magnetic field is varied. This phenomenon is found to be sensitive to the spontaneous magnetization orientation, and is attributed to the giant magnetic linear dichroism (MLD) effect in (Ga,Mn)As. Our findings suggest that this effect will enable the sensitive measurement of the dynamic phase of in-plane magnetization precession on picosecond time scale in the collective spin excitation in (Ga,Mn)As, thus enabling efficient and ultrafast magneto-optical detection for magnetization dynamics in ferromagnetic semiconductor-based spintronic devices. [ABSTRACT FROM AUTHOR]

We present a study of photoexcited magnetization dynamics in ferromagnetic (Ga,Mn)As films observed by time-resolved magneto-optical measurements. The magnetization precession triggered by linearly polarized optical pulses in the absence of an external field shows a strong dependence on photon frequency when the photoexcitation energy approaches the band edge of (Ga,Mn)As. This can be understood in terms of magnetic anisotropy modulation by both laser heating of the sample and by hole-induced nonthermal paths. Our findings provide a means for identifying the transition of laser-triggered magnetization dynamics from thermal to nonthermal mechanisms, a result that is of importance for ultrafast optical spin manipulation in ferromagnetic materials via nonthermal paths. [ABSTRACT FROM AUTHOR]

Tunneling magnetoresistance (TMR) observed in Fe/GaAlAs/GaMnAs magnetic tunnel junctions depends strongly on relative configuration of magnetizations in the GaMnAs and Fe layers. Using a series of field orientations, we show that non-collinear alignments of magnetization in this structure occur when the magnetic field is applied away from the easy axes of the magnetic layers; and we find that the values of TMR observed for non-collinear spin configurations are very different from those of collinear configurations. The observed behavior suggests the possibility of using this effect for multivalued magnetic memory devices. [ABSTRACT FROM AUTHOR]

The current state of information technology accentuates the dichotomy between processing and storage of information, with logical operations carried out by charge-based devices and non-volatile memory based on magnetic materials. The main obstacle for a wider use of magnetic materials for information processing is the lack of efficient control of magnetization. Reorientation of magnetic domains is conventionally carried out by non-local external magnetic fields or by externally polarized currents. The efficiency of the latter approach is enhanced in materials where ferromagnetism is carrier-mediated, because in such materials the control of carrier polarization provides an alternative means for manipulating the orientation of magnetic domains. In some crystalline conductors, the charge current couples to the spins by means of intrinsic spin–orbit interactions, thus generating non-equilibrium electron spin polarization tunable by local electric fields. Here, we show that magnetization can be reversibly manipulated by the spin–orbit-induced polarization of carrier spins generated by the injection of unpolarized currents. Specifically, we demonstrate domain rotation and hysteretic switching of magnetization between two orthogonal easy axes in a model ferromagnetic semiconductor. [ABSTRACT FROM AUTHOR]