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In this work we performed a detailed numerical analysis to investigate the static and dynamic magnetic properties of hexagonal cells of square and circular cobalt nanodots as a function of the distance between them and the external magnetic field to which they are subjected. By simulating hysteresis curves with the external magnetic field applied parallel and perpendicular to the plane of these nanostructures, we can conclude that the cobalt nanodots presented a significant perpendicular magnetic anisotropy. We also obtained that the coercivity increases with decreasing volume, which implies that the circular dots have a higher coercivity than the square dots. Furthermore, we studied the dynamic susceptibility of these systems and found that it is possible to control both the position and the number of resonance peaks by controlling the geometry and the distance between the magnetic nanodots. This work provides useful information on the behaviour of cobalt nanodot arrays, opening paths for the design and improvement of two-dimensional technological devices. [ABSTRACT FROM AUTHOR]

In this work, we report the synthesis as well as the structural and magnetic characterization of the three perovskites La 2 MnB'O 6 (B' = Ti, Zr, and Hf). Interestingly, only La 2 MnTiO 6 crystallizes in the monoclinic double perovskite space group P 2 1 / n , with a complete rocksalt order of the B-site cations, whereas La 2 MnZrO 6 and La 2 MnHfO 6 crystallize in the orthorhombic simple perovskite space group Pbnm , with complete disorder in the B site. Moreover, the magnetic susceptibility at low temperatures shows clear antiferromagnetic transitions below 10 K for the three compounds, but only the Ti-based perovskite has long-range magnetic ordering. The latter compound has an antiferromagnetic type-II structure described by the P S -1 magnetic space group, while the other two have a spin-glass behavior below the transition temperature due to both spin disorder and competing superexchange interactions in the systems. This is the first time that two of the three studied compounds were synthesized (B' = Zr and Hf) and the first time that the whole series is described in thorough detail using symmetry-adapted refinements and magnetic crystallography.