Accession Number : AD0613577

Title :   MOSSBAUER STUDIES ON IRON IN THE PEROVSKITES LA1-XSR-XFEO3 (0< OR = X< OR = 1). CONDITION FOR MAXIMUM RESONANCE ABSORPTION PEAK IN A SINGLELINE MOSSBAUER ABSORPTION,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE LAB FOR INSULATION RESEARCH

Personal Author(s) : Shimony,Uri ; Knudsen,Jens M.

Report Date : FEB 1965

Pagination or Media Count : 49

Abstract : Mossbauer spectra of the perovskite series La1-xSr-x FeO-y (0. 0< or = x < or = 1.0; y Approx. < 3) were obtained with Fe(57) as the photon-emitting and absorbing nucleus and analyzed in detail. The Neel temperature of antiferromagnetic LaFeO3 decreases with increasing Sr concentration, in agreement with previous reports. That of antiferromagnetic SrFeO2.5 (brownmillerite structure) also decreases as oxygen is introduced to transform it to perovskite SrFeO3. Characteristic Fe(4+) lines, identified for compounds of high x, have isomer shifts between +0.10 and +0.20 mm/sec relative to a source of Co(57) in stainless steel Type 310. However, spectra of compounds of intermediate x indicate the existence of an intermediate Fe(3+ to 4+) state, and a correlation between the total isomer shift of a compound and its Fe(4+) content was attempted. With increasing x a significant discontinuity in the total isomer shift, corresponding to a transition from magnetic order to disorder, was found. Line widths vary around 0.40 mm/sec (compared with 0.26 mm/sec, the narrowest line obtainable in the present setup) and show broadening in a sample fired for a short time. The temperature effect was used to calculate the specific heat. (Author)

Descriptors :   (*IRON, MOSSBAUER EFFECT), (*DIELECTRICS, MOSSBAUER EFFECT), (*MOSSBAUER EFFECT, ABSORPTION SPECTRA), LANTHANUM COMPOUNDS, STRONTIUM COMPOUNDS, FERRATES, ANTIFERROMAGNETISM, CRYOGENICS, PHASE STUDIES, SOLID SOLUTIONS, LINE SPECTRA, SPECIFIC HEAT, CRYSTAL STRUCTURE, NUCLEAR ISOMERS, NUCLEAR RESONANCE

Distribution Statement : APPROVED FOR PUBLIC RELEASE