F. S. Razavi

Epitaxial strain induced metal insulator transition in La0.9Sr0.1MnO3 and La0.88Sr0.1MnO3 thin films

We are reporting an unexpected metal insulator transition at the ferromagnetic phase-transition temperature for thin films of La0.9Sr0.1MnO3 ( 50 nm), similar to the single crystal, no such transition is observed below TC. Additionally, we observe the suppression of the features associated with charge or orbital ordering in intentionally La-deficient thin films of La0.88Sr0.1MnO3 (<75 nm). In thin films, transmission electron microscopy reveals a compressive strain due to the epitaxial growth, that is, lattice parameters adopt those of the cubic lattice of SrTiO3. As the film thickness increases, coherent microtwinning is observed in the films and the films relax to a orthorhombic structure.

Spin-glass-like behavior in Y2Mo2O7, a concentrated, crystalline system with negligible apparent disorder

Abstract The pyrochlore-structure material Y2Mo2O7 is apparently a well-ordered crystalline compound with a concentrated magnetic, Mo4+, sublattice. Yet, the magnetic properties are typical of spin glasses. There is a maximum in the zero-field cooled susceptibility at 22K, no long range magnetic order at 4.2 K, sample-history dependent behavior below 22 K and Curie-Weiss law deviations below 80 K. The effective magnetic moment is 2.06 μ B Mo 4+ and θc = −61 K . The spin-glass-like properties are attributed to a frustrated Mo4+ sublattice with competing ferromagnetic and antiferromagnetic interactions.

Preparation and Magnetic Properties of Iron(3+) Spin-Crossover Complexes Bearing a Thiophene Substituent: Toward Multifunctional Metallopolymers

The synthesis of a new 3-ethynylthienyl-substituted QsalH ligand (QsalH is the short form for N-(8-quinolyl)salicylaldimine) (ThEQsalH 3), and the preparation, electronic, and magnetic properties of three homoleptic and cationic iron(3+) complexes containing this ligand with PF(6)(-) 4, SCN(-) 5, and ClO(4)(-) 6 counteranions are reported. In all three complexes a spin-crossover is observed in the solid state by variable temperature magnetic susceptibility measurements and Mossbauer spectroscopy, indicating that the synthetic modification of the QsalH ligand has not significantly altered the electronics at the metal center. This includes the observation of a very rare S = 5/2 to 3/2 spin-crossover in a non-porphyrin iron(3+) complex 5. The molecular structure and magnetic properties of an unusual iron(2+) complex 7 generated by reduction of complex 6 serendipitously during a recrystallization attempt in aerobic acetone solution is also reported. Complexes 4-6 feature iron(3+) reduction and oxidation of the thiophene ring at potentials of approximately -0.7 and +1.2 V (vs Fc), respectively.

Periodic microtwinning as a possible mechanism for the accommodation of the epitaxial film-substrate mismatch in the La1−xSrxMnO3/SrTiO3 system

Abstract The structure and microstructure of laser-deposited La1−xSr x MnO3(x ≈ 0.1) films on SrTiO3(100) single-crystal substrates have been studied by means of electron diffraction and high-resolution transmission electron microscopy. The film–substrate interfaces are found to be perfectly coherent and in particular to be free of interfacial dislocations, the small misfit being accommodated either elastically or by the formation of periodic microtwins. Cross-section as well as plan-view specimens of films of four different thicknesses (9, 50, 100 and 220 nm) were studied in detail. The thinnest films were found to be rhombohedral when present as coherent epitaxial films in cross-section specimens, the misfit being accommodated by periodic microtwinning. When released from their substrate, as in plan-view specimens, films of the same thickness are domain-fragmented orthorhombic. It is suggested that the misfit stresses tend to favour a microtwinned rhombohedral structure, whereas unstressed films of the same thickness, released from the substrate, tend to become domain-fragmented orthorhombic. The observations illustrate in a striking manner the effect of misfit stresses on the microstructure of thin epitaxial films, explaining also the dependence of the physical properties on the film thickness and on the misfit.

Specific heat of the Ca-intercalated graphite superconductor CaC6.

The superconducting state of Ca-intercalated graphite CaC6 has been investigated by specific heat measurements. The characteristic anomaly at the superconducting transition (Tc = 11.4 K) indicates clearly the bulk nature of the superconductivity. The temperature and magnetic field dependence of the electronic specific heat are consistent with a fully gapped superconducting order parameter. The estimated electron-phonon coupling constant is lambda = 0.70 +/- 0.04, suggesting that the relatively high Tc of CaC6 can be explained within the intermediate coupling BCS approach.

Effect of pressure on superconducting Ca-intercalated graphite CaC6

The pressure effect on the superconducting transition temperature (

Tunable magnetic and magnetocaloric properties of La0.6Sr0.4MnO3 nanoparticles

T_c

The thickness dependence of the effect of pressures on magnetic and electronic properties of thin films of La2/3Ca1/3MnO3

) of the newly-discovered Ca-intercalated graphite compound CaC

Placing a crown on DyIII – a dual property LnIII crown ether complex displaying optical properties and SMM behaviour

_6

Multifunctional nanoparticles for rapid bacterial capture, detection, and decontamination

has been investigated up to