Crystal Structure and Magnetic Properties of SrCaMnGaO5+δ

✍ Scribed by Peter D. Battle; Anthony M.T. Bell; Stephen J. Blundell; Amalia I. Coldea; Daniel J. Gallon; Francis L. Pratt; Matthew J. Rosseinsky; Christopher A. Steer

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 524 KB
• Volume: 167
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2002.9641

✦ Synopsis

The room-temperature crystal structure of the brownmillerite SrCaMnGaO 5+d (d ¼ 0:035) has been refined from neutron powder diffraction data; space group Ima2, a ¼ 15:7817ð6Þ; b ¼ 5:4925ð2Þ, c ¼ 5:3196ð2Þ ( A. Mn and Ga occupy 99.0(2)% of the 6-and 4-coordinate sites, respectively. A combination of magnetometry, neutron diffraction and lSR spectroscopy has shown that the compound orders magnetically at 180 K, and that the low-temperature phase has a G-type antiferromagnetic structure, with an ordered magnetic moment of 3.30(2) l B per Mn at 2 K. Displaced hysteresis loops provide evidence that the atomic moment has an additional, glassy component. Magnetometry shows that significant short-range magnetic interactions persist above 180 K, and lSR that the spin fluctuations are thermally activated in this temperature region. The compound is an electrical insulator which at 159 K shows an unusually large magnetoresistance of 85% in 6 T, increasing to 90% in 13 T.