Hard x-ray photoemission spectroscopy of the ferrimagnetic series Gd6(Mn1−xFex)23

Abstract

We study the evolution of the electronic structure of the intermetallic series Gd 6 (Mn 1−x Fe x ) 23 , x = 0.0-0.75, which shows nonmonotonic ferrimagnetic ordering temperatures T C but with a systematic reduction of the total bulk magnetization upon increasing Fe content, x. We have carried out hard x-ray photoemission spectroscopy to elucidate the relation between electronic structure and properties of the series. The Gd 3d and Gd 4d corelevel spectra indicate trivalent Gd 3+ multiplets in the intermediate-coupling scheme with features due to L-S and j-J coupling. The Fe 2p core levels show asymmetric single peak metal-like spectra, while the Mn 2p core levels show asymmetric doublet peaks. The relative intensities of the Mn 2p doublets as a function of x indicate occupancy changes of distinct crystallographic sites associated with Mn up-spin and down-spin states. The valence band spectra identify the Gd 4 f states at high binding energies (∼7.4 eV). The Mn 3d states occur at the Fermi level and as a broad feature between 2 and 5 eV binding energy in Gd 6 Mn 23 . Upon substitution, the Fe 3d states show up as small shifts to higher binding energies compared to Mn 3d states. The Fe 3s and Mn 3s spectra show exchange split peaks, allowing an estimate of the Mn and Fe magnetic moments using a Van Vleck analysis, which also provides a quantification of occupancy changes with x. The overall results are consistent with the bulk net magnetization, indicating that Mn up-spin sites become Fe down-spin sites on substitution, while the nonmonotonic T C originates in a change from Mn sublattice to Fe sublattice derived ordering.

Element-specific Curie temperatures and Heisenberg criticality in ferrimagnetic Gd6(Mn1−xFex)23 via Kouvel-Fisher analysis

“…It is also noted that even if we assume that all the substituted Fe for x = 0.2 occupies the 'f 1 , f 2 ' sites with µ Fe aligned antiparallel to µ Gd , M X Tot is consistent with M B Tot because µ Mn shows a switching, indicating a breakdown of the magnetization as an additive mixture of the parent compounds; this behaviour has not been recognized earlier in the absence of element-specific magnetic moments. Moreover, the results are fairly consistent with the change in magnetic moments µ Fe and µ Mn estimated from the 3s core-level HAXPES 55 , which also showed a monotonic change in total magnetization.…”

“…2a) is slightly higher compared to ND results. The magnetic moments are also consistent with values estimated from a Van Vleck analysis of 3s core-level photoemission spectra 55 . The average magnetic moment of Gd is calculated to be μ Gd = +7.18 μ B , also in good agreement with the localized Gd 3+ 4f 7 configuration as well as the result from sum rule analysis discussed above.…”

“…The calculations identify the contributions of the Gd 4f, Gd 5d, Fe 4s, and Fe 3d PDOS contributions to the experimental spectrum. d The valence band spin-integrated total DOS of Gd 6 (Mn 0.25 Fe 0.75 ) 23 is approximated by an additive mixture of 25% Gd 6 Mn 23 and 75% Gd 6 Fe 23 calculations, plotted together with the bulk-sensitive valence band spectrum measured by HAXPES 55 .…”

Crucial role of d−d Coulomb correlations in the magnetocaloric ferrimagnets Gd6(Mn1−xNguyen, Yang, Wang et al. 2024Phys. Rev. BSelf Cite2000View full textAdd to dashboardCite

“…The Mn 2p spectrum consists of the 2p 3/2 and 2p 1/2 features at a binding energy (BE) of 638.4 and 649.7 eV. The Mn 2p 3/2 and 2p 1/2 features could be resolved into doublets and fitted with asymmetric Doniach-Sunjic line shapes, consistent with HAXPES results reported recently [58]. It was shown that the relative intensity of the doublets follows the Mn up-spin and down spin site occupancies which change systematically with Fe content x in Gd 6 (Mn 1−x Fe x ) 23 .…”

“…2(a) and confirm their Mn 3d character. The weaker intensity in the 0.5 eV CIS spectra is attributed to the admixture of Gd 5d states at and near E F , as was discussed in HAXPES studies [58].…”