Effect of pressure on the magnetic properties of YNi5, LaNi5, and CeNi5

The effect of pressure on the electronic structure and magnetic properties of the compounds YNi5, LaNi5, and CeNi5 is studied. Large magnetovolume effects of magnitude dlnχ∕dlnV≃4–7 are found for the magnetic susceptibility χ of these systems at low temperatures. Experimental data and “first principles” calculations of the electronic structure and paramagnetic contributions to the susceptibility indicate that YNi5, LaNi5, and CeNi5 are close to a quantum critical point. It is found that the van Vleck orbital contribution to the magnetic susceptibility is 15–20% in these exchange-enhanced paramagnetic materials and should be taken into account in analyzing experimental data on χ and dlnχ∕dlnV. Calculations of the magnetic-field induced moments for atoms in the unit cell of YNi5 reveal an inhomogeneous distribution of the magnetization density and a nontrivial competition between the spin and orbital moments.