The electronic structure of UCoGe by<i>ab initio</i>calculations and XPS experiment

Samsel‐Czekała, M.; Elgazzar, S.; Oppeneer, Peter M.; Talik, E.; Walerczyk, Wiktoria; Troć, R.

doi:10.1088/0953-8984/22/1/015503

Cited by 37 publications

(59 citation statements)

References 26 publications

(60 reference statements)

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“…2. The results are in good agreement with previous band structure calculations [12,[50][51][52][53]. The occupied part of the DOS can be decomposed into two regions.…”

Section: Band Structuresupporting

confidence: 91%

“…Band structure calculations [12] and neutron experiments [11] have endeavored to explore the orbital and spin part of the ordered moment, but contradictory results were published. On one hand, theoretical calculations in the LSDA approach [12] predict a small uranium moment (~0.1 µ B ) due to an almost cancellation of substantial orbital and spin moments, and unexpectedly a large cobalt moment (0.2-0.5 µ B ) either parallel or antiparallel to the U moment. On the other hand, comparison of NMR data of UCoGe led to conclude that the ferromagnetism in UCoGe originates predominantly from U 5f electrons at least at low field [13].…”

Section: Introductionmentioning

confidence: 99%

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Electronic and magnetic properties of the ferromagnetic superconductor UCoGe

Antonov

2017

Low Temperature Physics

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The electronic structure and x-ray magnetic circular dichroism (XMCD) spectra of the ferromagnetic superconductor UCoGe at the U N 4,5 , Ge and Co K and Co L 2,3 edges were investigated theoretically from first principles, using the fully relativistic Dirac linear muffin-tin orbital band structure method. The electronic structure is obtained with the local spin-density approximation (LSDA), as well as with a generalization of the LSDA+U method which takes into account the non-diagonal occupation matrix (in spin indexes) of localized electrons. A stable ferromagnetic ground state was found. The uranium total magnetic moment is quite small (about -0.171µ B ) in the LSDA approximation as a result of almost complete cancellation between the spin magnetic moment of 0.657 µ B and the opposite orbital magnetic moment of -0.828 µ B , resulting from strong spin-orbit coupling at the uranium site. Valency of U ion in UCoGe is close to 3+. The ratio orbital and spin magnetic moments M l /M s ranged from 1.163 in the GGA approach up to 2.456 for the LSDA+U calculations is smaller than the corresponding ratio for the free ion U 3+ value (2.60), it can indicate a significant delocalization of the 5f-electron states due to the hybridization of the U 5f electrons with the conduction band and Co 3d electrons. The line shape of the dichroic spectra at the U M 5 and M 4 edges predicted by considering the magneto-optical selection rules as well as the occupation and the energy sequence of the m j -projected partial densities of states. The theoretically calculated XMCD spectra at the U M 4,5 , Ge and Co K and Co L 2,3 edges are in good agreement with the experimentally measured spectra. PACS

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“…2. The results are in good agreement with previous band structure calculations [12,[50][51][52][53]. The occupied part of the DOS can be decomposed into two regions.…”

Section: Band Structuresupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Electronic and magnetic properties of the ferromagnetic superconductor UCoGe

Antonov

2017

Low Temperature Physics

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“…This is at variance with the electronic-structure calculations. [16][17][18] However, the PND data reveal that the Co moment is susceptible to a magnetic field, and magnetic moments on both the U and Co atoms, as predicted by the calculations, do occur in applied magnetic field. The small value of the Co moment in weak magnetic fields is in line with recent zero-field SR ͑Ref.…”

mentioning

confidence: 83%

“…In addition, a much larger moment Co ϳ 0.2-0.5 B is predicted at the Co atom. The magnetic moments on the U and Co sites are expected to orient parallel 16,18 or antiparallel 17 and consequently it is argued that the magnetic structure is quite complex and, for instance, magnetic stripe order 16 or an antiferromagnetic spin arrangement 17 have been proposed. In this Rapid Communication we report PND experiments on UCoGe conducted to identify the different contributions to the bulk magnetization in the normal phase ͓we apply a field B ʈ c larger than the upper critical field B c2 c Ӎ 0.5 T ͑Ref.…”

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confidence: 99%

Anomalous spin distribution in the superconducting ferromagnet UCoGe studied by polarized neutron diffraction

et al. 2010

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Anomalous spin distribution in the superconducting ferromagnet UCoGe studied by polarized neutron diffraction Prokeš, K.; de Visser, A.; Huang, Y.; Fåk, B.; Ressouche, E. General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. We report a polarized neutron-diffraction study conducted to reveal the nature of the weak ferromagnetic moment in the superconducting ferromagnet UCoGe. We find that the ordered moment in the normal phase in low magnetic fields ͑B ʈ c͒ is predominantly located at the U atom and has a magnitude of ϳ0.1 B at 3 T, in agreement with bulk magnetization data. By increasing the magnetic field the U moment grows to ϳ0.3 B in 12 T and most remarkably, induces a substantial moment ͑ϳ0.2 B ͒ on the Co atom directed antiparallel to the U moment. The anomalous polarizability of the Co 3d orbitals is unique among uranium intermetallics and might reflect the proximity to a magnetic quantum critical point of UCoGe in zero field.

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“…Theoretically calculated de Haas van Alphen frequencies in the ferromagnetic state of UCoGe which come from a closed Fermi surface for a field rotation from the c axis to ab axis show that the largest frequency of 3.72 kT at  = 0° is obtained for this geometry and it slightly decreases in value with increasing angle to 2.7 kT at  = 60° [16]. The observed frequency decreases above  = 30°, accompanied with the currently observed OHE (which is linked to the type of carriers and their number) decrease at angles above  = 52° suggest possible small shrinkage of the volume of the Fermi surface.…”

Section: B Bmentioning

confidence: 90%

HALL EFFECT STUDIES OF THE SUPERCONDUCTING FERROMAGNET UCoGe

Krstovska

Steven²,

Kiswandhi³

et al. 2017

Contributions

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We find that the Hall effect in a single crystal of UCoGe varies as a function of the angle  between the applied magnetic field and the easy magnetic axis up to fields of 18 T at 0.2 K, i.e. in the region where both superconductivity and ferromagnetic order coexist. Instead of following the conventional cos dependence the two components that comprise the total Hall resistance, the anomalous and ordinary Hall effect, exhibit quite an unusual behavior with the field direction. The anomalous Hall effect is found to be determined by the parallel component of the magnetization. We suggest that the field induced changes in magnetization due to the field rotation play an important role in the observed unusual behavior. The ordinary Hall effect cannot be described by the simple relation to the perpendicular component of the magnetic field implying that this component of the Hall effect may be also affected by the variations in magnetization at the characteristic field (kink field). A field induced moment polarization is also observed in Hall effect as in magnetoresistance, which advances previous findings in UCoGe. The Hall effect slope reverses sign at the kink field indicative of small but possible Fermi surface reconstruction around this field. Our findings show that in UCoGe multiple mechanisms contribute to the observed field induced moment polarization at the kink field.

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The electronic structure of UCoGe byab initiocalculations and XPS experiment

Cited by 37 publications

References 26 publications

Electronic and magnetic properties of the ferromagnetic superconductor UCoGe

Electronic and magnetic properties of the ferromagnetic superconductor UCoGe

Anomalous spin distribution in the superconducting ferromagnet UCoGe studied by polarized neutron diffraction

HALL EFFECT STUDIES OF THE SUPERCONDUCTING FERROMAGNET UCoGe

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