Fully electrically read-write device out of a ferromagnetic semiconductor

We report the realization of a read-write device out of the ferromagnetic semiconductor (Ga,Mn)As as the first step to fundamentally new information processing paradigm. Writing the magnetic state is achieved by current-induced switching and read-out of the state is done by the means of the tunneling anisotropic magneto resistance (TAMR) effect. This one bit demonstrator device can be used to design a electrically programmable memory and logic device.Comment: 4 pages, 4 figure

Controlled skyrmion nucleation in extended magnetic layers using a nanocontact geometry

We propose and numerically simulate a spintronic device layout consisting of a nanocontact on top of an extended Co/Pt bilayer. The interfacial Dzyaloshinskii-Moriya interaction in such bilayer systems can lead to the possible existence of metastable skyrmions. A small dc current injected through the nanocontact enables the manipulation of the size as well as the annihilation of an initially present skyrmion, while ps-long current pulses allow for the controlled nucleation of single skyrmions underneath the nanocontact. The results are obtained from micromagnetic simulations and can be potentially used for future magnetic storage implementations

Super-harmonic injection locking of nano-contact spin-torque vortex oscillators

Super-harmonic injection locking of single nano-contact (NC) spin-torque vortex oscillators (STVOs) subject to a small microwave current has been explored. Frequency locking was observed up to the fourth harmonic of the STVO fundamental frequency $f_{0}$ in microwave magneto-electronic measurements. The large frequency tunability of the STVO with respect to $f_{0}$ allowed the device to be locked to multiple sub-harmonics of the microwave frequency $f_{RF}$, or to the same sub-harmonic over a wide range of $f_{RF}$ by tuning the DC current. In general, analysis of the locking range, linewidth, and amplitude showed that the locking efficiency decreased as the harmonic number increased, as expected for harmonic synchronization of a non-linear oscillator. Time-resolved scanning Kerr microscopy (TRSKM) revealed significant differences in the spatial character of the magnetization dynamics of states locked to the fundamental and harmonic frequencies, suggesting significant differences in the core trajectories within the same device. Super-harmonic injection locking of a NC-STVO may open up possibilities for devices such as nanoscale frequency dividers, while differences in the core trajectory may allow mutual synchronisation to be achieved in multi-oscillator networks by tuning the spatial character of the dynamics within shared magnetic layers.Comment: 21 pages, 8 figure

Direct observation of magnetization dynamics generated by nano-contact spin-torque vortex oscillators

Time-resolved scanning Kerr microscopy has been used to directly image the magnetization dynamics of nano-contact (NC) spin-torque vortex oscillators (STVOs) when phase-locked to an injected microwave (RF) current. The Kerr images reveal free layer magnetization dynamics that extend outside the NC footprint, where they cannot be detected electrically, but which are crucial to phase-lock STVOs that share common magnetic layers. For a single NC, dynamics were observed not only when the STVO frequency was fully locked to that of the RF current, but also for a partially locked state characterized by periodic changes in the core trajectory at the RF frequency. For a pair of NCs, images reveal the spatial character of dynamics that electrical measurements show to have enhanced amplitude and reduced linewidth. Insight gained from these images may improve understanding of the conditions required for mutual phase-locking of multiple STVOs, and hence enhanced microwave power emission.Comment: 10 pages, 3 figure

Enhancement of spin mixing conductance in La_0.7Sr_0.3MnO₃/LaNiO₃/SrRuO₃ heterostructures

Spin pumping and the effective spin-mixing conductance in heterostructures based on magnetic oxide trilayers composed of La0.7Sr0.3MnO3 (LSMO), LaNiO3 (LNO), and SrRuO3 (SRO) are investigated. The heterostructures serve as a model system for an estimation of the effective spin-mixing conductance at the different interfaces. The results show that by introducing a LNO interlayer between LSMO and SRO, the total effective spin-mixing conductance increases due to the much more favorable interface of LSMO/LNO with respect to the LSMO/SRO interface. Nevertheless, the spin current into the SRO does not decrease because of the spin diffusion length of λLNO ≈ 3.2nm in the LNO. This value is two times higher than that of SRO. The results show the potential of using oxide interfaces to tune the effective spin-mixing conductance in heterostructures and to bring novel functionalities into spintronics by implementing complex oxides