Spin fluctuations in ferromagneticZrZn2

The magnetic properties of ferromagnetic ${\mathrm{ZrZn}}_2$ are calculated at zero and at finite temperatures. For this, use is made of the local spin-density functional approximation and an ab initio spin-fluctuation theory, which has its roots in the Ginzburg-Landau theory. In particular, the total energy, the magnetic moments, the density of states, and the band structure are obtained as functions of the pressure. Noncollinear spin arrangements yield the necessary information to calculate the pressure dependence of the nonuniform susceptibility at zero temperature as well as the Curie temperature and the Curie-Weiss susceptibility at high temperatures. The role of dissipation is discussed critically and comparison with recent experimental data for ${\mathrm{ZrZn}}_2$ shows satisfactory agreement.