Neutron Powder Diffraction Studies in CaMn1-xCuxO3 (x = 0, 0.20)

Department of Physics, Indian Institute of Technology Guwahati, Guwahati-781 039* Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati, India** Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai-400 085, India***
○S Ravi* Manoranjan Kar** S.M. Borah* P.S.R Krishna***

CaMn1-xCuxO3 compounds have been prepared in single phase form for x = 0 to 0.30 by following solid state route. The X-ray diffraction (XRD) patterns recorded at room temperature could be analyzed using Pbnm space group. AC susceptibility measurements show that these materials exhibit antiferromagnetic transitions with Neel temperature TN = 125K. The Neutron Powder Diffraction (NPD) patterns were recorded for x = 0 and 0.20 samples at different temperatures down to 11K. All the observed crystallographic peaks could be refined to Pbnm space group by using Rietveld refinement technique and no structural transition has been observed down to 11K. The lattice parameters for x = 0 and 0.20 samples at room temperature (300K) are found to be a=5.264, b=5.275 & c=7.451Å and, a=5.267, b=5.280 & c=7.459Å respectively. An additional peak at 2θ = 16.70 has been observed below TN and its intensity was found to increase with decrease in temperature. It could be indexed to magnetic (101) plane. The magnetic structure has been refined by assuming the propagation vector k = (0,0,0), since the magnetic peaks appear exactly on crystallographic plane. The magnetic ordering is found to be G-type arrangement. The magnetic moment of Mn ions was refined and its temperature variation shows a magnetic ordering at T = TN. The typical value of magnetic moment of Mn ion is 2.69μB for x = 0 sample at 11K.