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Article Dans Une Revue Journal of Physics: Condensed Matter Année : 2020

Correlations between stacked structures and weak itinerant magnetic properties of La2−xYxNi7 compounds

Résumé

Hexagonal La2Ni7 and rhombohedral Y2Ni7 are weak itinerant antiferromagnet (wAFM) and ferromagnet (wFM), respectively. To follow the evolution between these two compounds, the crystal structure and magnetic properties of A2B7 intermetallic compounds (A = La, Y, B = Ni) have been investigated combining X-ray powder diffraction and magnetic measurements. The La2-xYxNi7 intermetallic compounds with 0 ≤ x ≤ 1 crystallize in the hexagonal Ce2Ni7-type structure with Y preferentially located in the [A2B4] units. The compounds with larger Y content (1.2 ≤ x < 2) crystallize in both hexagonal and rhombohedral (Gd2Co7-type) structures with a substitution of Y for La in both [A2B4] and [AB5] units. Y2Ni7 crystallizes in the rhombohedral structure only. The average cell volume decreases linearly versus Y content, whereas the c/a ratio presents a minimum at x = 1 due to geometric constrains. The magnetic properties are strongly dependent on the structure type and the Y content. La2Ni7 displays a complex metamagnetic behavior with split AFM peaks. Compounds with x = 0.25 and 0.5 display a wAFM ground state and two metamagnetic transitions, the first one towards an intermediate wAFM state and the second one towards a FM state. TN and the second critical field µ0Hc2 increase with the Y content, indicating a stabilization of the AFM state. LaYNi7, which is as the boundary between the two structure types, presents a very wFM state at low field and an AFM state as the applied field increases. All the compounds with x > 1, and which contains a rhombohedral phase are wFM with TC = 53(2) K. In addition to the experimental studies, first principles calculations using spin polarization have been performed to interpret the evolution of structural phase stability for 0 ≤ x ≤ 2.
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hal-02919132 , version 1 (21-08-2020)

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Valérie Paul-Boncour, Jean-Claude Crivello, Nicolas Madern, Junxian Zhang, L. V. B. Diop, et al.. Correlations between stacked structures and weak itinerant magnetic properties of La2−xYxNi7 compounds. Journal of Physics: Condensed Matter, 2020, 32 (41), pp.415804. ⟨10.1088/1361-648X/ab9d4c⟩. ⟨hal-02919132⟩
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