Magnetic ordering of Mo2NiB2-type {Gd, Tb, Dy)2Co2Al compounds by magnetization and neutron diffraction studyстатья
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Дата последнего поиска статьи во внешних источниках: 17 октября 2017 г.
Аннотация:The magnetic ordering of Mo2NiB2-type {Gd, Tb, Dy}2Co2Al (Immm, No. 71, oI10) compounds has been established using bulk magnetic measurements and neutron diffraction study. Polycrystalline Gd2Co2Al, Tb2Co2Al and Dy2Co2Al undergo ferrimagnetic transitions (TC) at 78 K, 98 K and 58 K, respectively, and low-temperature field induced transition (Tm) around 15 K, 20 K and 15 K, respectively. Between Tm and TC Gd2Co2Al, Tb2Co2Al and Dy2Co2Al are soft ferrimagnets. Below Tm Gd2Co2Al is soft ferrimagnet, whereas Tb2Co2Al and Dy2Co2Al exhibit permanent magnet properties with residual magnetization per rare earth of 4.95 mB and 4.8 mB, respectively, and large coercive field of 72 kOe and 22 kOe, respectively, at 2 K.
The magnetocaloric effects of Gd2Co2Al, Tb2Co2Al and Dy2Co2Al were calculated in terms of isothermal magnetic entropy change and they reach maximum values of -10.4 J/kgK, -7.6 J/kgK and -6.6 J/kgK for a field change of 50 kOe near 75 K, 98 K and 58 K, respectively. Low-temperature transition of Gd2Co2Al is followed by the magnetic entropy change of -2.9 J/kgK in a field change of 50 kOe at 15 K. Low temperature magnetic ordering with enhanced anisotropic effects in Tb2Co2Al and Dy2Co2Al is accompanied by a positive magnetocaloric effect with isothermal magnetic entropy changes of +19.9 J/kgK at 20 K (field change 0-50 kOe) and +2.7 J/kgK at 15 K (field change 0-10 kOe), respectively.
Neutron diffraction study shows that, in zero applied field, Tb2Co2Al exhibits c-axis ferrimagnetic ordering with magnetic space group Immm' and propagation vector K0 = [0, 0, 0] below TCND ~ 111 K with MTb = 8.86(15) mB and MCo = 0.26(2) mB at 2 K.