Stability of the Gd Magnetic Moment to the 500 GPa Regime

Abstract

The evolution of the magnetic moment and various features of the electronic structure of fcc Gd are followed to reduced volume V/Vo = 0.125 using the LDA+U correlated band method. The stability of the moment is substantial; crude estimates of this signature of a possible ``Mott transition'' in the 4f system suggest a critical pressure Pc 500 GPa. The $4f$ occupation is found to increase under pressure due to broadening and lowering of the minority states. This trend is consistent with the interpretation of x-ray spectra of Maddox et al. across the volume collapse transition at 59 GPa, and tends to support their suggestion that the delocalization of the 4f states in Gd differs from the original abrupt picture, being instead a process that occurs over an extended range of pressure.