Polycrystalline Zn1−xCoxO diluted magnetic semiconductors have been prepared by coprecipitation technique in the concentration range 0⩽x⩽0.1. Structure, composition analysis, and optical absorption measurements revealed that cobalt is incorporated into the lattice, as Co2+ substituting Zn2+ ions, forming a solid solution with wurtzite structure instead of Co precipitates. Room- and low-temperature magnetization measurements reveal a paramagnetic behavior for the Co-doped ZnO samples with a paramagnetic Co amount smaller than the nominal concentration. χT versus T evidenced that the remaining Co is antiferromagnetically coupled through oxygen. This is further supported by a simple model that shows that as the Co concentration increases the amount of nearest neighbors Co atoms increases thus giving antiferromagnetic coupling and reducing the paramagnetic contribution.

We report on the growth by evaporation under high vacuum of high-quality thin films of Fe(phen)2(NCS)2 (phen=1,10-phenanthroline) that maintain the expected electronic structure down to a thickness of 10 nm and that exhibit a temperature-driven spin transition. We have investigated the current-voltage characteristics of a device based on such films. From the space charge-limited current regime, we deduce a mobility of 6.5x10-6 cm2/V?s that is similar to the low-range mobility measured on the widely studied tris(8-hydroxyquinoline)aluminium organic semiconductor. This work paves the way for multifunctional molecular devices based on spin-crossover complexes

hydrogen bonds · magnetic properties · metalorganic frameworks · multiferroic compounds · solid-state structuresThe realization of ever smaller tunable devices is a major challenge in nanoelectronics; as a result, considerable efforts have been devoted to multifunctional materials in the last few years. Multiferroic compounds in which magnetic and electric properties coexist have received much attention. The observation of combined weak ferromagnetism and antiferroelectric order in a metal-organic framework (MOF) from Jain et al. illustrates a new route towards multiferroic systems that significantly differs from usually reported studies. [1] Multiferroic materials present at least two coexisting orders among the electric, magnetic and/or elastic ones. The most appealing combination to date involves electric and magnetic orders, as it opens great perspectives in terms of applications, especially in the field of spintronics.[2] A clear distinction has to be made between systems exhibiting independent electric and magnetic orders and those featuring a magneto-electric coupling, both of which are promising in terms of applications. The former allows, for example, the conception of a four-state memory, [3] but the greatest promise is likely to be held by magneto-electric compounds, for they give access to a new type of control of magnetization by an electric field in spintronics devices. [4] The heart of the problem currently is to find examples of multiferroic/magnetoelectric materials. One option is, of course, to combine the properties of two separate materials, one being ferromagnetic, the other ferroelectric, in a nanostructured composite material.[5] The coupling between both, which allows their mutual control, is usually carried out indirectly through strain by magneto-and electro-striction, which results in slow switching and fatigue phenomena. Intrinsic multiferroics are thus highly desirable, although, as mentioned by Jain et al., electric and magnetic orders tend to be mutually exclusive. Indeed, the presence of d electrons of transition metal ions, which are required to stabilize ferromagnetism, inhibits hybridization with the p orbitals of the surrounding oxygen anions, and thus displacement of the cations necessary for the establishment of a ferroelectric order. [6] Intrinsic multiferroic materials, which are scarce, are generally classified according to the mechanism responsible for ferroelectricity: in proper ferroelectrics, spontaneous polarization appears as being itself the order parameter, whereas in improper ferroelectrics, it only appears as a by product in a phase transition governed by another order parameter. [7] For the former, the magnetic and electric orders are usually due to distinct cations, and the magnetoelectric coupling is generally weak. The prototypical compound is BiFeO 3 (BFO), in which 3d electrons of the iron(III) cations are responsible for magnetization, whereas ferroelectricity originates from a structural instability caused by the hybridization between the oxygen 2p and th...

Non-Ising-like 180° ferroelectric domain wall architecture and domain distribution in tetragonal PbZr Ti O thin films are probed using a combination of optical second harmonic generation and scanning transmission electron microscopy. In the remnant state, a specific nonlinear optical signature of tilted 180° domain walls corresponding to a mixed Ising-Néel-type rotation of polarization across the wall is shown.