2000/07/14 by C. D. Ling, Chris D. Ling, J. E. Millburn +6 · 4 citations
Chemistry · Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Chemistry #Colossal magnetoresistance #Condensed matter physics #Crystal structure #Crystallography #Ferromagnetism #Magnetic and transport properties of perovskites and related materials #Magnetic field #Magnetic structure #Magnetization #Magnetoresistance #Manganite #Materials science #Neutron diffraction #Orthorhombic crystal system #Phase (matter) #Phase diagram #Physics #Quantum mechanics #Rare-earth and actinide compounds #Tetragonal crystal system #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevb.62.15096
32 pages, 13 figures, submitted to Phys. Rev. B
arxiv created 2000/07/14 · openalex publication_date 2000/12/01 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The crystallographic and magnetic phase diagram of the n=2 layered manganite La_2\ensuremath-2xSr1+2xMn2O7 in the region x>~0.5 has been studied using temperature-dependent neutron powder diffraction. The magnetic phase diagram reveals a progression of ordered magnetic structures generally paralleling that of three-dimensional (3D) perovskites with similar electronic doping: A (0.5<~x<~0.66)\ensuremath→C (0.75<~x<~0.90)\ensuremath→G (0.90<~x<~1.0). However, the quasi-2D structure amplifies this progression to expose features of manganite physics uniquely accessible in the layered systems: (i) a ``frustrated'' region between the A and C regimes where no long-range magnetic order is observed; (ii) magnetic polytypism arising from weak interbilayer magnetic exchange in the type-C regime; and (iii) a tetragonal-to-orthorhombic phase transition whose temperature evolution directly measures ordering of d_3y2\ensuremath-r2 orbitals in the a\ensuremath-b plane. This orbital-ordering transition is precursory to type-C magnetic ordering, where ferromagnetic rods lie parallel to the b axis. These observations support the notion that eg orbital polarization is the driving force behind magnetic spin ordering. Finally, in the crossover region between type-C and type-G states, we see some evidence for the development of local type-C clusters embedded in a type-G framework, directly addressing proposals of similar short-range magnetic ordering in highly doped La_1\ensuremath-xCaxMnO3 perovskites.