Mo2NiB2-type {Gd,Tb,Dy)2Ni2.35Si0.65 and La2Ni3-type {Dy,Ho}2Ni2.5Si0.5 compounds: Crystal structure and magnetic propertiesстатья
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Дата последнего поиска статьи во внешних источниках: 9 июня 2015 г.
Аннотация:The crystal structure of new Mo2NiB2-type {Gd, Tb, Dy}2Ni2.35Si0.65 (Immm, No. 71, oI10) and La2Ni3-type {Dy, Ho}2Ni2.5Si0.5 (Cmce No. 64, oC20) compounds has been established using powder X-ray diffraction studies.
Magnetization measurements show that the Mo2NiB2-type Gd2Ni2.35Si0.65 undergoes a ferromagnetic transition at ~66 K, whereas isostructural Tb2Ni2.35Si0.65 shows an antiferromagnetic transition at ~52 K and a field-induced metamagnetic transition at low temperatures. Neutron diffraction study shows that, in zero applied field, Tb2Ni2.35Si0.65 exhibits c-axis antiferromagnetic order with propagation vector K = [1/2, 0, 1/2] below its magnetic ordering temperature and Tb magnetic moment reaches a value of 8.32(5) mB at 2 K.
The La2Ni3-type Dy2Ni2.5Si0.5 exhibits ferromagnetic like transition at ~42 K with coexisting antiferromagnetic interactions and field induced metamagnetic transition below ~17 K.
The magnetocaloric effect of Gd2Ni2.35Si0.65, Tb2Ni2.35Si0.65 and Dy2Ni2.5Si0.5 is calculated in terms of isothermal magnetic entropy change and it reaches a maximum value of -14.3 J/kgK, -5.3 J/kgK and –10.3 J/kgK for a field change of 50 kOe near 66 K, 52 K and 42 K, respectively. Low temperature magnetic ordering with enhanced anisotropic effects in Tb2Ni2.35Si0.65 and Dy2Ni2.35Si0.65 is accompanied by a positive magnetocaloric effect with isothermal magnetic entropy changes of +12.8 J/kgK and ~+9.9 J/kgK, respectively at 7 K for a field change of 50 kOe.