Magnetic and crystal structure correlations in PrMn1.5Co0.5Ge2:: a synchrotron diffraction study

Structure details of PrMn2-xCoxGe2, x = 0.5, with the tetragonal ThCr2Si2-type structure have been studied by high-resolution synchrotron powder diffraction. Unit cell parameters a and c, unit cell volume V, c/a, (partial derivativea/partial derivativex)(T) and (partial derivativec/partial derivativex)(T) were determined from Rietveld refinements in the temperature range 10-300 K. The average composition <x> = 0.49(4) is determined based on a detailed diffraction profile analysis. Our measurements indicate three anomalies in the c/a ratio, (partial derivativea/partial derivativex)(T) and (partial derivativec/partial derivativex)(T) at a temperature of about 150 K, which is very close to the transition temperature from antiferromagnetic to ferromagnetic intralayer ordering. (C) 2002 Elsevier Science Ltd. All rights reserved.