Crystal structures and magnetic properties of Ca2-xSrxMnO4

We prepared Ruddlesden-Popper-type layered perovskites Ca2-xSrxMnO4 (x = 0- 2.0 at 0.25 intervals), Their precise crystal structures at room temperatur e and at 10 K were determined from both the X-ray and the neutron diffracti on measurements. The compounds for x = 0 and 0.25 have a tetragonal system with the space group I4(1)/acd (No. 142), The compounds for x = 0.5-2.0 hav e a tetragonal system with the space group I4/mmm (No. 139), Magnetic susce ptibility measurements have been performed for all the compounds in the tem perature range between 5 and 350 K. The temperature-dependent magnetic susc eptibilities were measured under zero-field-cooled (ZFC) and field-cooled ( FC) conditions at an applied field of 1000 G. A dramatic difference in magn etic susceptibilities between ZFC and FC was observed below the Neel temper atures for Ca2MnO4 and Ca1.75Sr0.25MnO4, which shows the onset of a ferroma gnetic moment below these temperatures. This moment is caused by the Dzyalo shinsky-Moriya interaction. Magnetic structures of Ca2-xSrxMnO4 (x = 0.0, 0 .5, 1.0, and 1.5) solid solutions at 10 K have been determined by the neutr on diffraction measurements. The nearest-neighbor Mn4+ ions are coupled ant iferromagnetically in the (001) planes and the spins are parallel to the c axis. (C) 1999 Academic Press.