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We report on the electrical transport properties of Nb based Josephson junctions with Pt/Co 68 B 32 /Pt ferromagnetic barriers. The barriers exhibit perpendicular magnetic anisotropy, which has the main advantage for potential applications over magnetisation in-plane systems of not affecting the Fraunhofer response of the junction. In addition, we report that there is no magnetic dead layer at the Pt/Co 68 B 32 interfaces, allowing us to study barriers with ultra-thin Co 68 B 32 . In the junctions, we observe that the magnitude of the critical current oscillates with increasing thickness of the Co 68 B 32 strong ferromagnetic alloy layer. The oscillations are attributed to the ground state phase difference across the junctions being modified from zero to π . The multiple oscillations in the thickness range 0.2 ⩽ d CoB ⩽ 1.4 nm suggests that we have access to the first zero- π and π -zero phase transitions. Our results fuel the development of low-temperature memory devices based on ferromagnetic Josephson junctions. [ABSTRACT FROM AUTHOR]

We demonstrate a Josephson junction with a weak link containing two ferromagnets with perpendicular magnetic anisotropy and independent switching fields in which the critical current can be set by the mutual orientation of the two layers. Such pseudospin-valve Josephson junctions are a candidate cryogenic memory in an all superconducting computational scheme. Here, we use Pt/Co/Pt/CoB/Pt as the weak link of the junction with d Co = 0.6 nm , d CoB = 0.3 nm , and d Pt = 5 nm and obtain a 60% change in the critical current for the two magnetization configurations of the pseudospin-valve. Ferromagnets with perpendicular magnetic anisotropy have advantages over magnetization in-plane systems, which have been exclusively considered at this point, as, in principle, the magnetization and magnetic switching of layers in the junction should not affect the in-plane magnetic flux. [ABSTRACT FROM AUTHOR]

We use ferromagnetic resonance to study the current-induced torques in YIG/heavy metal bilayers. YIG samples with thickness varying from 14.8 nm to 80 nm, with the Pt or Ta thin film on top, are measured by applying a microwave current into the heavy metals and measuring the longitudinal DC voltage generated by both spin rectification and spin pumping. From a symmetry analysis of the FMR lineshape and its dependence on YIG thickness, we deduce that the Oersted field dominates over spin-transfer torque in driving magnetization dynamics. [ABSTRACT FROM AUTHOR]

The response of Y3Fe5O12/Cu/Ni81Fe19 trilayer structures to excitation by a femtosecond laser pulse has been studied in optical pump-probe experiments and compared with the response of Y3Fe5O12 (YIG) and Ni81Fe19 reference samples. The optical pump induces a partial demagnetization of the Ni81Fe19, a large thermal gradient within the YIG, and temperature differences across the interfaces within the sample stack. When a moderate magnetic field is applied close to normal to the sample plane, so as to quasialign the YIG magnetization with the field and cant the Ni81Fe19 magnetization from the plane, ultrafast demagnetization initiates precession of the Ni81Fe19 magnetization. The transient temperature profile within the samples has been modeled using a one-dimensional finite-element computational model of heat conduction, while the magnetization dynamics are well described by a macrospin solution of the Landau-Lifshitz-Gilbert equation. The precessional response of the Ni81Fe19 layers within the trilayers and the Ni81Fe19 reference sample are very similar for pump fluences of up to 1.5mJ/cm², beyond which irreversible changes to the magnetic properties of the films are observed. These results suggest that the spin Seebeck effect is ineffective in modifying the precessional dynamics of the present YIG/Cu/Ni81Fe19 samples when subject to ultrafast optical excitation. [ABSTRACT FROM AUTHOR]