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Title: Sign reversal of the MN-O bond compressibility in La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} below T{sub C}: Exchange striction in the ferromagnetic state

Sign reversal of the MN-O bond compressibility in La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} below T{sub C}: Exchange striction in the ferromagnetic state The crystal structure of the layered perovskite La{sub 1.2}Sr{sub 1.8}Mn{sub 2}O{sub 7} has been studied under hydrostatic pressure up to {approximately} 6 kbar, in the paramagnetic and ferromagnetic states, with neutron powder diffraction. The compressibility of the Mn-O apical bonds in the double layer of MnO{sub 6} octahedra changes sign from the paramagnetic insulator (PI) to the ferromagnetic metal (FM) state; in the Fm state the Mn-O-Mn linkage between MnO{sub 2} planes expands under applied pressure, whereas they contract in the PI state. This counterintuative behavior is interpreted in terms of exchange striction, which reflect the competition between super- and double-exchange. An increase of the Mn-moment with applied pressure in the FM state is consistent with a positive dT{sub C}/dP, as well as a cant angle {theta}{sub 0} between the magnetizations of neighboring MnO{sub 2} sheets that decreases with pressure.
Authors: ; ; ; ; ;
Publication Date:
OSTI Identifier:OSTI ID: 521660
Report Number(s):ANL/MSD/CP--91963; CONF-9703106--1
ON: DE97007006; CNN: Grant NSF DMR 91-20000; TRN: 97:018424
DOE Contract Number:W-31109-ENG-38
Resource Type:Conference
Resource Relation:Conference: American Physical Society meeting, Kansas City, MO (United States), 17-21 Mar 1997; Other Information: PBD: Mar 1997
Research Org:Argonne National Lab., IL (United States)
Sponsoring Org:USDOE Office of Energy Research, Washington, DC (United States);National Science Foundation, Washington, DC (United States);Welch (Robert A.) Foundation, Houston, TX (United States)
Country of Publication:United States
Language:English
Subject: 36 MATERIALS SCIENCE; CRYSTAL STRUCTURE; LANTHANUM OXIDES; STRONTIUM OXIDES; MANGANESE OXIDES; PHYSICAL PROPERTIES; PRESSURE DEPENDENCE; CURIE POINT; CHEMICAL BONDS; TEMPERATURE DEPENDENCE