Uranium ferromagnet with negligible magnetocrystalline anisotropy: U4Ru7Ge6

Kód výsledku v 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>

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

Uranium ferromagnet with negligible magnetocrystalline anisotropy: U4Ru7Ge6

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

Uranium ferromagnet with negligible magnetocrystalline anisotropy: U4Ru7Ge6

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

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

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

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

Rok uplatnění

2017

Kód důvěrnosti údajů

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

Název periodika

Physical Review B

ISSN

2469-9950

e-ISSN

—

Svazek periodika

95

Číslo periodika v rámci svazku

8

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

9

Strana od-do

—

Kód UT WoS článku

000395992000006

EID výsledku v databázi Scopus

2-s2.0-85014588028