CRYSTAL-STRUCTURES OF A2FECL5.H2O (A=RB+,CS+) AND FIELD-DEPENDENT SUPERCONDUCTING SUSCEPTOMETER MEASUREMENTS

Crystal structures and low field principal crystal axis magnetic measurements are reported for the antiferromagnetic iron (III) salts A 2FeCl5·H2O; A=Rb+, Cs +. The two compounds undergo a zero field paramagnetic to antiferromagnetic phase transition at 6.5 K (A=Cs+) and 10.05 K (A=Rb+). The spin flop magnetic phase is observed in high field measurements. The magnetic field-temperature phase diagrams are reported. All magnetic measurements were recorded on a superconducting susceptometer. The bicritical points are 6.25 K, 14.5 kOe (A=Cs+), 9.75 K, 17.8 KOe (A=Rb+). Crystal data for Cs2FeCl5· H2O: space group Cmcm, Z=4, a=7.442(3) Å, b=17.307(7) Å, c=8.077(7) Å, V=1040 Å3, R=5.2%, 561 reflections. Crystal data for Rb2FeCl5·H2O, space group Pnma, Z=4, a=13.825(4) Å, b=9.918(3) Å, c=7.100(2) Å, V=4.9 Å3, 5.7%, 712 reflections. © 1979 American Institute of Physics.