Uranium ferromagnet with negligible magnetocrystalline anisotropy: U4Ru7Ge6

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F17%3A10363589" target="_blank" >RIV/00216208:11320/17:10363589 - isvavai.cz</a>

Result on the web

<a href="http://dx.doi.org/10.1103/PhysRevB.95.085142" target="_blank" >http://dx.doi.org/10.1103/PhysRevB.95.085142</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1103/PhysRevB.95.085142" target="_blank" >10.1103/PhysRevB.95.085142</a>

Result language

angličtina

Original language name

Uranium ferromagnet with negligible magnetocrystalline anisotropy: U4Ru7Ge6

Original language description

Strong magnetocrystalline anisotropy (MA) is a well-known property of uranium compounds. The almost isotropic ferromagnetism in U4Ru7Ge6 reported in this paper represents a striking exception. We present results for magnetization, ac susceptibility, thermal expansion, specific heat, and electrical resistivity measurements performed on a U4Ru7Ge6 single crystal at various temperatures and magnetic fields; we discuss the results in relation to first-principles electronic structure calculations. U4Ru7Ge6 behaves as an itinerant 5f -electron ferromagnet (T-C = 10.7K, mu(S) = 0.85 mu(B)/f. u. at 1.9K). The ground-state easy magnetization direction is along the [111] axis of the cubic lattice. The anisotropy field mu H-0(a) along the [001] direction is only about 0.3T, which is at least three orders of magnitude smaller than for other U ferromagnets. At T-r = 5.9K the easy magnetization direction changes to [001], and remains [001] up to T-C. This transition is due to a change in magnetic symmetry, and is quite apparent in the low-field magnetization, ac susceptibility, and thermal expansion data, whereas only weak anomalies are observed at T-r in the temperature dependence of the specific heat and electrical resistivity. The magnetoelastic interaction induces a rhombohedral (tetragonal) distortion of the paramagnetic cubic crystal lattice in the case of the [111] ([001]) easy magnetization direction. The rhombohedral distortion is connected with two crystallographically inequivalentUsites. Our density functional theory calculations, including spin-orbit interaction (SOI) of the U 5f electrons, also produces two inequivalent U sites, because SOI leads to a reduction of the symmetry of the former cubic structure. The calculated ground state is in agreement with the experimentally observed [111] easy magnetization direction. The first excited state has moments along the [001] direction, which agrees with the moment orientation forT &gt; T-r r. The energy of the first excited state is 0.9meV above the ground state, which is comparable to the value of 0.51 meV, corresponding to k(B)T(r). We propose that weak MA of the U4Ru7Ge6 compound is due to the lack of direct overlap of the 5f orbitals of the nearest U ions, which is screened out by the closed Ru and Ge cuboctahedra coordinating each U ion.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10302 - Condensed matter physics (including formerly solid state physics, supercond.)

Project

Result was created during the realization of more than one project. More information in the Projects tab.

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2017

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Physical Review B

ISSN

2469-9950

e-ISSN

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Volume of the periodical

95

Issue of the periodical within the volume

8

Country of publishing house

US - UNITED STATES

Number of pages

9

Pages from-to

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UT code for WoS article

000395992000006

EID of the result in the Scopus database

2-s2.0-85014588028