The rare earth contribution to the magnetocrystalline anisotropy in RCo 5 intermetallics

Abstract

The magnetocrystalline anisotropy (MCA) energy of the 4f ions in the RCo 5 series has been calculated within the single-ion approximation. The Hamiltonian of the 4f ion in the form H = α J «r 4 f 2 a ̊ A 2 0O 2 0 + 2(g - 1)μ B JH ex has been invoked. The ground state multiplet given by Hund's rule for the trivalent rare earth ions has been dealt with. The zero temperature value and the temperature dependence of the MCA energy of the 4f ions have been satisfactorily described by only two parameters A 2 0 = -750 K A ̊ -2 and H ex = 150 T for the whole series. The temperature of magnetic moment reorientation is correctly reproduced for Tb, Dy and Ho compounds. The higher valency of approximately +3.5 of the Pr and Nd ion is inferred. The conduction electron contribution to the crystalline electric field at the R site is evaluated to be comparable to that given by the rare earth contribution. The value of the exchange field adjusted in the paper is about twice as small as it has been though so far.