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Article Dans Une Revue Physical Review B Année : 2020

Relationship between magnetic ordering and gigantic magnetocaloric effect in HoB2 studied by neutron diffraction experiment

Résumé

Recently, HoB 2 was discovered to undergo a gigantic magnetic entropy change; the largest |ΔS M| = 40.1 J kg −1 K −1 (0.35 J cm −3 K −1) in magnetocaloric materials studied for hydrogen liquefaction [P. Baptista de Castro et al., NPG Asia Mater. 12, 35 (2020)]. In this study, in order to investigate the origin of the gigantic |ΔS M| in HoB2 , we studied the magnetic orderings by neutron diffraction with an enriched powder sample of Ho11B2. Our experimental results showed the onset of ferromagnetic long-range order below T C = 15 K. For the second phase transition at T 2 = 11 K, the spin reorientation occurs, and the temperature dependence of the total magnetic moment of Ho 3+ shows a kink anomaly, which is typically seen in compounds with quadrupolar ordering. In addition, the temperature dependence of the ferromagnetic short-range order above T C is strongly related to that of the magnetic entropy change in HoB 2. These results infer that the gigantic |ΔS M| in HoB2 is caused by (i) the spin reorientation transition, which is likely associated with quadrupolar ordering, giving the additional contribution to |ΔS M| at the lower phase transition temperature, T 2 = 11 K, and (ii) the large FM fluctuation above T C with origins in the strong suppression of the FM long-range order.
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Dates et versions

hal-04143410 , version 1 (27-06-2023)

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Noriki Terada, Kensei Terashima, Pedro Baptista de Castro, Claire Colin, Hiroaki Mamiya, et al.. Relationship between magnetic ordering and gigantic magnetocaloric effect in HoB2 studied by neutron diffraction experiment. Physical Review B, 2020, 102 (9), pp.094435. ⟨10.1103/physrevb.102.094435⟩. ⟨hal-04143410⟩

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