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The perpendicular shape anisotropy-spin transfer torque-magnetic random access memories (PSA-STT-MRAMs) take advantage of the nanopillar free-layer geometry for securing a good thermal stability factor from the shape anisotropy of the nanomagnet. Such a concept is particularly well-suited for small junctions down to a few nanometers. At such a volume size, the nanopillar can be effectively modeled as a Stoner–Wohlfarth particle, and the shape anisotropy scales with the spontaneous magnetization by ∼ M s 2. For almost all ferromagnets, M s is a strong function of temperature; therefore, the temperature-dependent shape anisotropy is an important factor to be considered in any modeling of the temperature-dependent performance of PSA-STT-MRAMs. In this work, we summarize and discuss various possible temperature-dependent contributions to the thermal stability factor and coercivity of the PSA-STT-MRAMs by modeling and comparing different temperature scaling and parameters. We reveal nontrivial corrections to the thermal stability factor by considering both temperature-dependent shape and interfacial anisotropies. The coercivity, blocking temperature, and electrical switching characteristics that resulted from incorporating such a temperature dependence are also discussed, in conjugation with the nanomagnet dimension and coherence volume. [ABSTRACT FROM AUTHOR]

We demonstrate the electrical detection of magnon–magnon hybrid dynamics in yttrium iron garnet/Permalloy (YIG/Py) thin film bilayer devices. Direct microwave current injection through the conductive Py layer excites the hybrid dynamics consisting of the uniform mode of Py and the first standing spin wave (n = 1) mode of YIG, which are coupled via interfacial exchange. Both the two hybrid modes, with Py- or YIG-dominated excitations, can be detected via the spin rectification signals from the conductive Py layer, providing phase resolution of the coupled dynamics. The phase characterization is also applied to a nonlocally excited Py device, revealing the additional phase shift due to the perpendicular Oersted field. Our results provide a device platform for exploring hybrid magnonic dynamics and probing their phases, which are crucial for implementing coherent information processing with magnon excitations. [ABSTRACT FROM AUTHOR]

We demonstrate the detection of phase-resolved magnetization dynamics with combinatorial magneto-optic Kerr and Faraday effects. The method uses a continuous-wave laser that is amplitude-modulated at the spin dynamic frequencies and thus allows for coherent tracking of the spin dynamics, akin a “lock-in”-type measurement. In particular, our method, using a single 1550 nm wavelength, probes simultaneously the ferromagnetic (FM) resonance of Y3Fe5O12 (YIG) and Permalloy (Py = Ni80Fe20) in a YIG-Py heterostructure. The fiber-based magneto-optic components also have the advantage of being made into a compact, tabletop or even portable system with yet robust measurement performances. We believe that our method will be found useful in studying hybrid quantum magnonic systems and/or investigating phase-resolved spin dynamics in nanomagnet structures involving both FM insulators and metals. [ABSTRACT FROM AUTHOR]

We report the construction and characterization of a comprehensive magnonic-opto-electronic oscillator (MOEO) system based on 1550-nm photonics and yttrium iron garnet (YIG) magnonics. The system exhibits a rich and synergistic parameter space because of the ability to control individual photonic, electronic, and magnonic components. Taking advantage of the spin wave dispersion of YIG, the frequency self-generation as well as the related nonlinear processes becomes sensitive to the external magnetic field. Besides being known as a band-pass filter and a delay element, the YIG delay line possesses spin wave modes that can be controlled to mix with the optoelectronic modes to generate higher-order harmonic beating modes. With the high sensitivity and external tunability, the MOEO system may find usefulness in sensing applications in magnetism and spintronics beyond optoelectronics and photonics. [ABSTRACT FROM AUTHOR]

Commercially prepared spherical zirconia (ZrO2) nanoparticles with an average particle diameter of 5 nm and functionalized with a hydrocarbon ligand were dispersed in a polyalphaolefin (PAO) base oil, producing a 10-nm stabilized zirconia nanofluid. The resulting nanofluid's properties were characterized, including thermal conductivity and viscosity. A preliminary study of the nanofluid's ability to generate protective tribofilms was conducted. Long-term stability was verified using dynamic light scattering (DLS) and average particle size was quantified as a function of time. A 10 wt% ZrO2 nanofluid maintained a 10-nm average particle size over 25 months, with no signs of agglomeration or sedimentation, and redispersion was not necessary before analysis. The tribological performance of several concentrations of ZrO2 nanofluids wasdisc characterized with a ball-on-disc tribometer. Tribofilm growth over time was collected via optical interference imaging. Friction data collected over time are also reported. Nanoparticle concentration was varied to understand its effect on tribofilm growth. The ZrO2 tribofilm morphology and chemistry were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). [ABSTRACT FROM AUTHOR]