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

TL;DR

This paper demonstrates that magnetic polarization can be induced in the non-magnetic $J=0$ ground state of americium when embedded in a ferromagnetic matrix, using x-ray magnetic circular dichroism to analyze the magnetic moments.

Contribution

It provides experimental evidence of induced magnetism in AmFe$_2$ and discusses the magnetic dipole operator across the actinide series, revealing new insights into actinide magnetism.

Findings

Am$^{3+}$ exhibits induced magnetic moments in AmFe$_2$

The spin component is twice the orbital component in Am

The total Am moment opposes the Fe moment

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 AmFe$_2$. Since $\langle J_z \rangle$ = 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 $\langle T_{z} \rangle$ can be determined directly; we discuss the progression of the latter across the actinide series.