Measurements related to the magnetism of curium metal

Abstract

We report a series of measurements on a <1 mg sample of 248 Cm metal. Magnetization measurements are similar to those reported earlier. X-ray absorption and magnetic circular dichroism (XMCD) measurements at the ESRF synchrotron at the M 4,5 absorption edges show that the element has an orbital moment of ∼6% of the spin moment, and the two are parallel. This confirms the predictions of intermediate coupling, which has been suggested for Cm by other spectroscopies. In an XMCD measurement 2.5 years later, a field of 17 T was found to induce a larger induced signal (by a factor of ∼2) than that found earlier, indicating a change in the sample. We attribute this to the gradual loss of crystallinity with time since preparation, as a result of the damaged caused by fragments from the spontaneous fission within the sample itself. The final measurements aimed to determine the antiferromagnetic structure with resonant x rays were unable to observe any diffraction peaks from the sample. The ground-state antiferromagnetic structure remains unresolved.

X-ray synchrotron radiation studies of actinide materials

“…9 shows an overview of the XMCD signals measured at the M 5 and M 4 edges in ferromagnetic AnFe 2 (An = U, Np, Pu, Am) compounds (Wilhelm et al, 2013;Magnani et al, 2015). These spectra are compared with the XMCD signal measured for elemental curium (Lander et al, 2019). For convenience, the photon energy is set to zero at the M 5 edge and the amplitude at the M 4 edge is normalized to unity.…”

“…The available cryomagnet affords magnetic fields up to 17 T and a base temperature of about 2 K. The minimum mass of the sample depends on the magnetic susceptibility of the system. For elemental curium, data have been collected on a 0.55 mg sample of 248 Cm (Lander et al, 2019), whereas a sample mass of 16 mg was sufficient for Am in a sample of AmFe 2 (Magnani et al, 2015).…”

“…The spectra have been corrected for self-absorption effects and incomplete circular polarization of the incident beam. Adapted from Lander et al (2019).…”

Reexaming the ground state and magnetic properties of curium dioxide

“…As a consequence, Cm comes to be the first actinide element that exhibits magnetic ordering under ambient condition 5 . It has an antiferromagnetic ground state with large ordered moment µ eff ≈ 7.58 µ B 6,7 . Now let us focus on the actinide dioxides, AnO 2 , which crystallize in a cubic CaF 2 -like structure.…”

Emergence of quasiparticle multiplets in curium

“…Note that Cm is a highly radioactive and toxic element. It is not an easy task to carry out extensive experiments to study its electronic structures and the corresponding lattice properties 16 . Accordingly, theoretical calculations are necessary and become increasingly important in the last decades.…”