Magnetic properties of GdM compounds: role of d-electrons

Magnetic susceptibility of ferromagnetic GdM alloys (M = Mg, Zn, Cd, and Cu1-xGax) has been investigated under pressure for temperatures above TC. The evaluated pressure derivatives of the paramagnetic Curie temperature appeared to be remarkably different for isovalent GdM compounds. Analysis of the experimental data and results of ab initio electronic-structure calculations for GdMg and GdZn have revealed the essential role of 5d electrons as the mediators of exchange coupling in ferromagnetic GdM compounds. The pressure derivatives of TC were calculated by employing a spin fluctuation theory. As a result, a good agreement is found with the experimental data. (orig.)