Forskning ved Københavns Universitet - Københavns Universitet


Structural and magnetic states in layered manganites: An expanding view of the phase diagram

Publikation: Bidrag til tidsskriftKonferenceartikelForskningfagfællebedømt

Colossal magnetoresistive (CMR) manganites display a spectacular range of structural, magnetic, and electronic phases as a function of hole concentration, temperature, magnetic field, etc. Although the bulk of research has concentrated on the 3-D perovskite manganites, the ability to study anisotropic magnetic and electronic interactions made available in reduced dimensions has accelerated interest in the layered Ruddlesden-Popper (R-P) phases of the manganite class. The quest for understanding the coupling among lattice, spin, and electronic degrees of freedom (and dimensionality) is driven by the availability of high quality materials. In this talk, we will present recent results on synthesis and magnetic properties of layered manganites from the La2-2xSr1+2xMn2O7 series in the Mn4+-rich regime x > 0.5. This region of the composition diagram is populated by antiferromagnetic structures that evolve from the A-type layered order to G-type "rocksalt" order as x increases. Between these two regimes is a wide region (0.7 < x < 0.9) where an incommensurate magnetic structure is observed. The IC structure joins spin canting and phase separation as a mode for mixed-valent manganites to accommodate FM/AF competition. Transport in these materials is dominated by highly insulating behavior, although a region close to x = 0.5 exhibits metal-nonmetal transitions and an extreme sensitivity to oxygen content. We suggest two possible explanations for this transport behavior at doping just above x=0.5: localization by oxygen defects or charge ordering of Mn3+/Mn4+ sites.

TidsskriftMaterials Research Society Symposium - Proceedings
Sider (fra-til)315-326
Antal sider12
StatusUdgivet - 1 dec. 2000
BegivenhedMagnetoresistive Oxides and Related Materials - Boston, MA, USA
Varighed: 29 nov. 19992 dec. 1999


KonferenceMagnetoresistive Oxides and Related Materials
ByBoston, MA

ID: 204464711