Magnetic polarization of the americium $J = 0$ ground state in AmFe$_{2}$

Abstract

Trivalent americium has a non-magnetic (J = 0) ground state arising from the cancelation of the orbital and spin moments. However, magnetism can be induced by a large molecular field if Am 3+ is embedded in a ferromagnetic matrix. Using the technique of x-ray magnetic circular dichroism, we show that this is the case in AmFe2. Since Jz = 0, the spin component is exactly twice as large as the orbital one, the total Am moment is opposite to that of Fe, and the magnetic dipole operator Tz can be determined directly; we discuss the progression of the latter across the actinide series.