Simultaneous multitone microwave emission by dc-driven spintronic nano-element.

Current-induced self-sustained magnetization oscillations in spin-torque nano-oscillators (STNOs) are promising candidates for ultra-agile microwave sources or detectors. While usually STNOs behave as a monochromatic source, we report here clear bimodal simultaneous emission of incommensurate microwave oscillations in the frequency range of 6 to 10 gigahertz at femtowatt level power. These two tones correspond to two parametrically coupled eigenmodes with tunable splitting. The emission range is crucially sensitive to the change in hybridization of the eigenmodes of free and fixed layers, for instance, through a slight tilt of the applied magnetic field from the normal of the nanopillar. Our experimental findings are supported both analytically and by micromagnetic simulations, which ascribe the process to four-magnon scattering between a pair of radially symmetric magnon modes and a pair of magnon modes with opposite azimuthal index. Our findings pave the way for enhanced cognitive telecommunications and neuromorphic systems that use frequency multiplexing to improve communication performance.

Inducing Dzyaloshinskii-Moriya interaction in symmetrical multilayers using post annealing.

The interfacial Dzyaloshinskii-Moriya Interaction (iDMI) is an antisymmetric exchange interaction that is induced by the broken inversion symmetry at the interface of, e.g., a ferromagnet/heavy metal. Thus, the presence of iDMI is not expected in symmetrical multilayer stacks of such structures. Here, we use thermal annealing to induce the iDMI in a [Py/Pt]×10 symmetrical multilayer stack. Brillouin light scattering spectroscopy is used to directly evidence the iDMI induction in the annealed sample. Structural characterizations highlight the modified crystallinity as well as a higher surface roughness of the sample after annealing. First principles electronic structure calculations demonstrate a monotonic increase of the iDMI with the interfacial disorder due to the interdiffusion of atoms, depicting the possible origin of the induced iDMI. The presented method can be used to tune the iDMI strength in symmetric multilayers, which are the integral part of racetrack memories, magnonic devices as well as spin-orbitronic elements.

Designing magnetic droplet soliton nucleation employing spin polarizer.

We show by means of micromagnetic simulations that spin polarizer in nano-contact (NC) spin torque oscillators as the representative of the fixed layer in an orthogonal pseudo-spin valve can be employed to design and to control magnetic droplet soliton nucleation and dynamics. We found that using a tilted spin polarizer layer decreases the droplet nucleation time which is more suitable for high speed applications. However, a tilted spin polarizer increases the nucleation current and decreases the frequency stability of the droplet. Additionally, by driving the magnetization inhomogenously at the NC region, it is found that a tilted spin polarizer reduces the precession angle of the droplet and through an interplay with the Oersted field of the DC current, it breaks the spatial symmetry of the droplet profile. Our findings explore fundamental insight into nano-scale magnetic droplet soliton dynamics with potential tunability parameters for future microwave electronics.

Investigative for no-carrier-added 87m,gY production by the proton-induced on 89Y.

The radioisotope 87Y is one of the candidates for the SPECT and 87Y/87mSr generator due to its suitable half-life and decay properties. The proton-induced on the 89Y target can be used for the production of 87Y. The present perusal calculated the excitation function for the both 89Y(p,x)87m,gY direct reaction and decay of 87Zr via 89Y(p,3n)87Zr → 87mY → 87gY indirect reaction using the TALYS-1.8 code. To simulation the production of 87m,gY nuclide, the target thickness was designed based on the stopping power calculation by the SRIM-2013 code. The Monte Carlo code GEANT4 was used to simulate the transport of protons through the irradiation assembly. Then, the cumulative integral yield of the 87m,gY has been calculated directly after the decay of 87Zr radionuclide entirely. These results were in good agreement with the theoretical and reported experimental data. Eventually, the integral yield of the 87m,gY was calculated by the indirect method from 87Zr decay after separation the zirconium. This work provides the basis for theoretical appraisement of the use of no-carrier-added 87Y as radiopharmaceutical for the purpose of medical applications.

Production and modeling of radioactive gold nanoparticles in Tehran research reactor.

Gold has two medically useful radioactive isotopes, 198Au and 199Au, for locally irradiating and killing tumor cells. 198Au radionuclide has been produced through the irradiation of the pure gold via 197Au(n,γ)198Au reaction in the Tehran Research Reactor at a thermal neutron flux of 4.5×1013ncm-2s-1 for the different irradiation times. In this paper, the activity of 198Au radionuclide has been determined using MCNPX-2.6 and TALYS-1.6 codes and also the theoretical approach. The calculated results were compared with the corresponding experimental values. The calculated results were in good agreement with the experimental data, thus the used codes can be used as a powerful tool to predict and optimize production conditions in reactor.