M. R. Fitzsimmons

Metal-Insulator Transition and Its Relation to Magnetic Structure in (LaMnO3)2n/(SrMnO3)n Superlattices

Superlattices of (LaMnO3){2n}/(SrMnO3){n} (1<or=n<or=5), composed of the gapped insulators LaMnO3 and SrMnO3, undergo a metal-insulator transition as a function of n, being metallic for n<or=2 and insulating for n>or=3. Measurements of transport, magnetization, and polarized neutron reflectivity reveal that the ferromagnetism is relatively uniform in the metallic state, and is strongly modulated in the insulating state, being high in LaMnO3 and suppressed in SrMnO3. The modulation is consistent with a Mott transition driven by the proximity between the (LaMnO3)/(SrMnO3) interfaces. The insulating state for n>or=3 obeys variable range hopping at low temperatures. We suggest that this is due to states at the Fermi level that emerge at the (LaMnO3)/(SrMnO3) interfaces and are localized by disorder.

Epitaxial La0.5Sr0.5CoO3 thin films: Structure, magnetism, and transport

La1−xSrxCoO3 has received considerable attention in bulk form. This is due to interest in the fundamental magnetic properties (spin-state transitions and magnetic phase separation) as well as potential applications in ferroelectric memory and solid-oxide fuel cells. The structure and properties in thin film form are not well understood, and the influence of dimensional confinement on effects such as magnetic phase separation is unknown. Here, we report a comprehensive investigation of structure, magnetism, and transport in strained epitaxial La0.5Sr0.5CoO3 (001) films deposited on SrTiO3 (001) substrates by reactive dc magnetron sputtering. The crystalline quality, phase purity, strain state, oxygen stoichiometry, morphology, and magnetic and electronic properties of the epilayers are all probed and are found to be particularly sensitive to the total sputtering gas pressure and the ratio of reactive to inert gas (PO2/PAr). The various structure-property relationships are discussed in detail, particularly ...

Tunable (δπ, δπ)-type antiferromagnetic order in α-Fe(Te,Se) superconductors

Magnetic spin fluctuations is one candidate to produce the bosonic modes that mediate the superconductivity in the ferrous superconductors. Up until now, all of the LaOFeAs and BaFe2As2 structure types have simple commensurate magnetic ground states, as result of nesting Fermi surfaces. This type of spin-density-wave (SDW) magnetic order is known to be vulnerable to shifts in the Fermi surface when electronic densities are altered at the superconducting compositions. Superconductivity has more recently been discovered in alpha-Fe(Te,Se), whose electronically active antifluorite planes are isostructural to the FeAs layers found in the previous ferrous superconductors and share with them the same quasi-two-dimensional electronic structure. Here we report neutron scattering studies that reveal a unique complex incommensurate antiferromagnetic order in the parent compound alpha-FeTe. When the long-range magnetic order is suppressed by the isovalent substitution of Te with Se, short-range correlations survive in the superconducting phase.

Upper limit to magnetism in LaAlO3/SrTiO3 heterostructures.

Using polarized neutron reflectometry we measured the neutron spin-dependent reflectivity from four LaAlO(3)/SrTiO(3) superlattices. Our results imply that the upper limit for the magnetization averaged over the lateral dimensions of the sample induced by an 11 T magnetic field at 1.7 K is less than 2 G. SQUID magnetometry of the neutron superlattice samples sporadically finds an enhanced moment, possibly due to experimental artifacts. These observations set important restrictions on theories which imply a strongly enhanced magnetism at the interface between LaAlO(3) and SrTiO(3).

Magnetically asymmetric interfaces in a LaMnO 3 / SrMnO 3 superlattice due to structural asymmetries

Polarized neutron reflectivity measurements of a ferromagnetic

On the two-state microstructure of nanocrystalline chromium

{[{({\text{LaMnO}}_{3})}_{11.8}/{({\text{SrMnO}}_{3})}_{4.4}]}_{6}

The magnetization of a grain boundary in nickel

superlattice reveal a modulated magnetic structure with an enhanced magnetization at the interfaces where

Magnetic nonuniformity and thermal hysteresis of magnetism in a manganite thin film.

{\text{LaMnO}}_{3}

Effects of hydrogen/deuterium absorption on the magnetic properties of Co/Pd multilayers

was deposited on

Conduction properties of metal/organic monolayer/semiconductor heterostructures

{\text{SrMnO}}_{3}