No abstract

The study examines the relationship between the development of logical processes required in deductive reasoning and their ocmsions of use. Verbal syllogism problems were presented to 4-to 5-year-old children. The problems were systematically varied in content (fantasy premises; premises incongruent with real-world events; premises congruent with real-world events), form, and order of presentation of problem types. Results indicate that young children are capable of making deductive inferences required in solving syllogism problems, and that these abilities are displayed in constrained conditions. The relationship of the problem content to realworld knowledge and the sequence of presentation of the problem types affected the display of logical abilities.

Josephson junctions containing two ferromagnetic layers are being considered for use in cryogenic memory. Our group recently demonstrated that the ground-state phase difference across such a junction with carefully chosen layer thicknesses could be controllably toggled between zero and π by switching the relative magnetization directions of the two layers between the antiparallel and parallel configurations. However, several technological issues must be addressed before those junctions can be used in a large-scale memory. Many of these issues can be more easily studied in single junctions, rather than in the Superconducting QUantum Interference Device (SQUID) used for the phase-sensitive measurements. In this work, we report a comprehensive study of spin-valve junctions containing a Ni layer with a fixed thickness of 2.0 nm, and a NiFe layer of thickness varying between 1.1 and 1.8 nm in steps of 0.1 nm. We extract the field shift of the Fraunhofer patterns and the critical currents of the junctions in the parallel and antiparallel magnetic states, as well as the switching fields of both magnetic layers. We also report a partial study of similar junctions containing a slightly thinner Ni layer of 1.6 nm and the same range of NiFe thicknesses. These results represent the first step toward mapping out a "phase diagram" for phase-controllable spin-valve Josephson junctions as a function of the two magnetic layer thicknesses.

Josephson junctions containing ferromagnetic layers are of considerable interest for the development of practical cryogenic memory and superconducting qubits. Such junctions exhibit a ground-state phase shift of π for certain ranges of ferromagnetic layer thickness. We present studies of Nb based micron-scale ellipticallyshaped Josephson junctions containing ferromagnetic barriers of Ni 81 Fe 19 or Ni 65 Fe 15 Co 20 . By applying an external magnetic field, the critical current of the junctions are found to follow characteristic Fraunhofer patterns, and display sharp switching behavior suggestive of single-domain magnets. The high quality of the Fraunhofer patterns enables us to extract the maximum value of the critical current even when the peak is shifted significantly outside the range of the data due to the magnetic moment of the ferromagnetic layer. The maximum value of the critical current oscillates as a function of the ferromagnetic barrier thickness, indicating transitions in the phase difference across the junction between values of zero and π. We compare the data to previous work and to models of the 0-π transitions based on existing theories.

The phase state of a spin-triplet Josephson junction containing three ferromagnetic layers is magnetically controlled.