PaRMa - Highlights

 Entanglement is a crucial resource for quantum information processing and its quantification is of paramount importance in many areas of current research. We have showed that four-dimensional inelastic neutron scattering enables us to portray entanglement in weakly coupled molecular qubits and to quantify it.

Portraying entanglement between molecular qubits with four-dimensional inelastic neutron scattering, Nature Communications 8, 14543 (2017).

The discovery of magnetic bistability in Mn12 more than 20 years ago marked the birth of molecular magnetism. We have exploited four-dimensional inelastic neutron scattering to portray how individual spins fluctuate around the magnetic ground state, thus fixing the exchange couplings of Mn12 for the first time.

Magnetic Exchange Interactions in the Molecular Nanomagnet Mn12, Phys. Rev. Lett. 119, 217202 (2017). Cover paper.

We have introduced two schemes for implementing universal quantum gates with supramolecular compounds containing the Cr7Ni molecular rings. We have characterized the real systems and performed detailed calculations, based on the measured parameters and including decoherence, to demonstrate how the gates operate.

A modular design of molecular qubits to implement universal quantum gates, Nature Communications 7, 11377 (2016).

An innovative and versatile non-contact set up based on the mirage effect has been utilized for the direct measurements of the magnetocaloric effect induced by a milliseconds pulsed magnetic field of 1 T. This technique has been applied to a MnFeP_0.45As_0.55 sample, demonstrating the absence of kinetic constraints in the first-order phase transition of this sample induced on the milliseconds time scale.

Millisecond direct measurement of the magnetocaloric effect of a Fe2P-based compound by the mirage effect, Applied Physics Letters 108 (2016) 012407

We have analyzed the Heusler class of materials looking for systems presenting large ground-state moments, which can be stabilized into a fully austenite state with a second-order phase transition around RT. In particular, the composition Ni₂Mn_1.4In_0.6 has found to exhibit a large magnetic moment and a noticeable reversible magneto-caloric effect. Based on the overview of the existing similar Heusler compounds together with additional first-principles calculations, we explain the underlying mechanisms and point out a perspective for further improvements.

Large Magnetization and Reversible Magnetocaloric Effect at the Second-Order Magnetic Transition in Heusler Materials, Advanced Materials 28 (2016) 3321–3325

A quantum critical point is the condition where a second order phase transition takes place at zero temperature. In this case, properties are dominated by quantum (not thermal) fluctuations.  Other order parameters may supersede this purely quantum state. µSR and other experiments show that the ferromagnet LaCrGe3 would display such a transition under 2 GPa, but the order turns to antiferromagnetic just before. Muon DFT calculations help understanding µSR data.

Ferromagnetic Quantum Critical Point Avoided by the Appearance of Another Magnetic Phase in LaCrGe3 under Pressure, Phys. Rev. Lett. 117 (2016) 037207

F doped LaFeAsO is an unconventional superconductor. Tiny amounts (0.02%) of Mn replacing Fe are sufficient to kill superconductivity, restoring the same stripe antiferromagnetic order of the undoped parent compound. ⁷⁵As NMR is sensitive enough to show that two distinct regions exist: strongly modified, around each Mn impurity and normal stripe order, elsewhere.

Fast recovery of the stripe magnetic order by Mn/Fe substitution in F-doped LaFeAsO superconductors,   Phys. Rev. B 95 (2017) 180501(R)