The slow dynamics and concomitant memory ͑aging͒ effects seen in nanomagnetic systems are analyzed on the basis of two separate paradigms: superparamagnets and spin glasses. It is argued that in a large class of aging phenomena it suffices to invoke superparamagnetic relaxation of individual single domain particles but with a distribution of their sizes. Cases in which interactions and randomness are important in view of distinctive experimental signatures are also discussed.

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The global phase diagram in a five-dimensiona1 parameter space is described for a model which can be thought of as the "regular-solution" model of a ternary mixture or the mean-field approximation to a spin-1Ising ferromagnet with a general nearest-neighbor interaction (the Blurne-Capel model). The model possesses three fourth-order critical points (known from previous work) which are connected to a total of nine lines of tricritical points. Four manifolds of four-phase coexistence occur along with three manifolds of double critical points and six manifolds of critical double-end points, The locations of all significant features of the phase diagram are described qualitatively, and quantitative results are provided for some of the manifolds of lower dimension. Computational procedures are described which permit a detailed exploration of any portion of the phase diagram which may be of interest.

Among the perovskite oxide family, KTaO3 (KTO) has recently attracted considerable interest as a possible system for the realization of the Rashba effect. In this work, we improvise a novel conducting interface by juxtaposing KTO with another insulator, namely LaVO3 (LVO) and report planar Hall effect (PHE) and anisotropic magnetoresistance (AMR) measurements. This interface exhibits a signature of strong spin-orbit coupling. Our experimental observation of two fold AMR at low magnetic fields can be intuitively understood using a phenomenological theory for a Rashba spin-split system. At high fields (∼8 T), we see a two fold to four fold transition in the AMR that could not be explained using only Rashba spin-split energy spectra. We speculate that it might be generated through an intricate process arising from the interplay between strong spin-orbit coupling, broken inversion symmetery, relativistic conduction electron and possible uncompensated localized vanadium spins.