We report ac susceptibility and continuous wave and pulsed EPR experiments performed on GdW10 and GdW30 polyoxometalate clusters, in which a Gd3+ ion is coordinated to different polyoxometalate moieties. Despite the isotropic character of gadolinium as a free ion, these molecules show slow magnetic relaxation at very low temperatures, characteristic of single molecule magnets. For T≲200  mK, the spin-lattice relaxation becomes dominated by pure quantum tunneling events, with rates that agree quantitatively with those predicted by the Prokof'ev and Stamp model [Phys. Rev. Lett. 80, 5794 (1998)]. The sign of the magnetic anisotropy, the energy level splittings, and the tunneling rates strongly depend on the molecular structure. We argue that GdW30 molecules are also promising spin qubits with a coherence figure of merit Q(M)≳50.

Polyoxometalate single ion magnet [GdW 30 P 5 O 110 ] 12− (1) has been studied by generalized Rabi oscillation experiments. It was possible to increase the number of coherent rotations tenfold through matching the Rabi frequency with the frequency of the proton. Achieving high coherence with polyoxometalate chemistry, we show their excellent potential not only for the storage of quantum information but even for the realization of quantum algorithms.The ultimate state of the art of the miniaturization limit of nanospintronics is the manipulation of a single electron spin.[1] Single molecule magnets are perfect examples of such control and constitute the building blocks of molecular spintronics and quantum computing from the chemistry point of view. [2,3] Since molecular spins are quantum objects and not just classical binary memories, the greatest challenge is precisely the manipulation of this single spin during a sufficiently long time. In the terms of quantum computing, this means the preservation of quantum coherence, i.e. all the information of the wave function, during the application of many quantum gate operations. This is a daunting task, but fortunately chemistry can provide the basics for the rational design and optimization of the building-blocks with the aimed quantum behavior. [4] Among these building-blocks, magnetic polyoxometalates (POMs) combine a rich magnetochemistry with an arbitrarily low abundance of nuclear spins. From this point of view, these molecular metal oxides open the possibility of developing a large variety of molecular spintronic devices with a hardware intrinsically suited to preserve the electron spins quantum coherence.[5] Indeed, 0a Instituto de Ciencia Molecular, University of Valencia, c/Cat. José Beltrán, 46980, Paterna, Spain. the preservation of spin coherence is a formidable challenge for quantum computing applications.[3] (b) Moreover, decoherence is a problem of fundamental importance in physics, with practical impact of the relaxation processes in chemistry and engineering. [6] In this context, pulsed EPR is an excellent tool for the study of the coherent manipulation of magnetic systems. [7] Under ideal conditions, which include the absence of microwave radiation or under a short pulse sequence, the theory estimates that relaxation times of magnetic molecules are in the order of τ 2 =100-500 µs. [8] In real conditions these times are drastically reduced, specially when the spins are manipulated. The simplest quantum manipulation is known as Rabi oscillation and consists of a full two-way cycle between states A and B induced by a microwave field at the transition energy E AB . The experimental observation of these Rabi oscillations is therefore indicative of long coherence times. In fact, the number of Rabi oscillations is directly connected to the number of quantum operations that can be performed on the system, so strategies to extend this number are necessary.In a recent study of the molecular magnet [V IV 15 As III 6 O 42 (H 2 O] 6− (V 15 ), the decay t...

The magnetic linear dichroism of the gadolinium 4f core level is studied in a time-resolved photoemission experiment employing laser pump-and synchrotron-radiation probe pulses. Upon optical excitation of the 5d6s valence electrons with femtosecond laser pulses, the magnetic order in the 4f spin system is reduced. Remarkably, the linear dichroism remains at 80% of the equilibrium contrast while the lattice temperature reaches the Curie temperature due to electron-phonon scattering. Contrasting itinerant ferromagnets, this shows that equilibration between the lattice and spin subsystems takes in Gd about 80 ps and is established in parallel with heat diffusion.

Molecular magnetism is reaching a degree of development that will allow for the rational design of sophisticated systems.

The quest for a spin‐polarized organic light‐emitting diode (spin‐OLED) is a common goal in the emerging fields of molecular electronics and spintronics. In this device, two ferromagnetic (FM) electrodes are used to enhance the electroluminescence intensity of the OLED through a magnetic control of the spin polarization of the injected carriers. The major difficulty is that the driving voltage of an OLED device exceeds a few volts, while spin injection in organic materials is only efficient at low voltages. The fabrication of a spin‐OLED that uses a conjugated polymer as bipolar spin collector layer and ferromagnetic electrodes is reported here. Through a careful engineering of the organic/inorganic interfaces, it is succeeded in obtaining a light‐emitting device showing spin‐valve effects at high voltages (up to 14 V). This allows the detection of a magneto‐electroluminescence (MEL) enhancement on the order of a 2.4% at 9 V for the antiparallel (AP) configuration of the magnetic electrodes. This observation provides evidence for the long‐standing fundamental issue of injecting spins from magnetic electrodes into the frontier levels of a molecular semiconductor. The finding opens the way for the design of multifunctional devices coupling the light and the spin degrees of freedom.

The synthesis of ultrathin films (UTFs) of NiFe‐LDHs has been achieved by means of an in situ hydrothermal approach, leading to a flat disposition of the LDH crystallites on the substrate, in clear contrast to the most common perpendicular orientation reported to date. Experimental factors like time of synthesis or the nature of the substrate, seem to play a crucial role during the growing process. The 2D morphology of the NiFe‐LDH crystallites was kept after a calcination procedure, leading to a topotactic transformation into mixed‐metal oxide platelets. Hereby, in order to study the catalytic behavior of our samples, a chemical vapor deposition process is explored upon the as‐synthesized films. In presence of a carbon source (ethylene), these films catalyze a preferential low‐temperature (550 °C) growth of bamboo‐like carbon nanotubes, in stark contrast to the different mixture of carbon nanoforms obtained from the bulk samples. This work opens the door for the development of UTFs based on LDHs, which may be of utmost importance in a wide range of potential applications ranging from magnetic storage, catalysis or biomedical applications, to electrochemical batteries, anti‐corrosion and superhydrophobic coatings.

Electrodeposited thin films of the molecule‐based magnet Cr5.5(CN)12·11.5H2O exhibit a magneto‐optical Kerr effect (MOKE) with large coercive fields at 200 K. As the thickness of the films is reduced to the nanometer scale, the particle size decreases and the magneto‐optical hysteresis becomes relatively large.

We report a new in-tube solid phase microextraction approach named magnetic in-tube solid phase microextraction, magnetic-IT-SPME. Magnetic-IT-SPME has been developed, taking advantage of magnetic microfluidic principles with the aim to improve extraction efficiency of IT-SPME systems. First, a magnetic hybrid material formed by Fe(3)O(4) nanoparticles supported on SiO(2) was synthesized and immobilized in the surface of a bared fused silica capillary column to obtain a magnetic adsorbent extraction phase. The capillary column was placed inside a magnetic coil that allowed the application of a variable magnetic field. Acetylsalicylic acid, acetaminophen, atenolol, diclofenac, and ibuprofen were tested as target analytes. The application of a controlled magnetic field resulted in quantitative extraction efficiencies of the target analytes between 70 and 100%. These results demonstrated that magnetic forces solve the low extraction efficiency (10-30%) of IT-SPME systems, which is one of their main drawbacks.