Structural and magnetic properties of churchite-type REPO4·2H2O materials

The structural and magnetic properties of churchite-type REPO4·2H2O (RE ​= ​Gd to Lu) materials (low-temperature polymorph of the rare-earth phosphate family) are reported. The materials were synthesized at low temperatures (4 ​°C) using a precipitation method and the long-range and local structures were determined using powder XRD and XANES. The churchite materials crystallize in the monoclinic system (Space group – C2/c) and adopt a 2D layered structure with water occupying the interlayer regions. The churchite materials were found to transform to the xenotime structure at 300 ​°C. DC magnetization experiments reveal the absence of long-range magnetic ordering between 300 and 1.8 ​K. The effective magnetic moments (μeff) are similar to those of the free RE (RE ​= ​Gd, Tb, Dy, Ho, Er) ions. Figure Caption: Churchite structure transforms to xenotime structure upon heating. [Display omitted] •Study of the local structure of the churchite phases LnPO4.2H2O with Ln ​= ​Gd to Lu.•Local structure evolution from churchite to xenotime.•Temperature-dependent magnetizations of the churchite phase.