Neutron powder diffraction and magnetic phase diagram of RCo4Ga compounds (R=Y and Pr)

The crystallographic and magnetic properties of hexagonal RCo4Ga are presented (R=Y and Pr). X-ray diffraction investigations exhibit a CaCu5-type single phase for both compounds. Neutron powder diffraction experiments demonstrate that the Ga atoms preferentially occupy the 3g crystallographic site of the CaCu5 structure. Substitution of Ga for Co substantially decreases the mean Co magnetic moment, the Curie temperature, and the saturation magnetization. The magnetocrystalline anisotropy is also drastically changed upon Ga substitution. A.c. susceptibility measurements have evidenced a spin reorientation transition in PrCo4Ga. A detailed investigation of this phenomenon occurring in PrCo4Ga is presented. Neutron and X-ray powder diffraction experiments as well as magnetic measurements are combined in order to clarify the effects of the Ga substitution on the magnetocrystalline anisotropy and the spin reorientation transition. The magnetic phase diagram of RCo4Ga (R=Y and Pr) has been determined in the whole ordered temperature range. (C) 2002 Elsevier Science B.V. All rights reserved.