Magnetic ordering of Mo2NiB2-type {Gd, Tb, Dy)2Co2Al compounds by magnetization and neutron diffraction study

• Published in: Journal of magnetism and magnetic materials 2017-11, Vol.442, p.36-44
• Main Authors: Morozkin, A.V., Genchel, V.K., Garshev, A.V., Yapaskurt, V.O., Isnard, O., Yao, Jinlei, Nirmala, R., Quezado, S., Malik, S.K.
• Format: Article
• Language: English
• Subjects: Coercivity; Crystal structure; Dysprosium; Entropy; Ferrimagnetism; Gadolinium; Magnetic measurement; Magnetic properties; Magnetic structure; Magnetism; Magnetization; Magnetocaloric effect; Neutron diffraction; Polycrystals; Rare earth compounds; Temperature distribution; Terbium
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2017.06.090

[Display omitted] 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 78K, 98K and 58K, respectively, and low-temperature field induced transition (Tm) around 15K, 20K and 15K, 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 4.95B and 4.8B, respectively, and large coercive field of 72kOe and 22kOe, respectively, at 2K. The magnetocaloric effects of Gd2Co2Al, Tb2Co2Al and Dy2Co2Al were calculated in terms of isothermal magnetic entropy change and they reach maximum values of −10.4J/kgK, −7.6J/kgK and −6.6J/kgK for a field change of 50kOe near 75K, 98K and 58K, respectively. Low-temperature transition of Gd2Co2Al is followed by the magnetic entropy change of −2.9J/kg K in a field change of 50kOe at 15K. 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 +19.9J/kgK at 20K (field change 0–50kOe) and +2.7J/kgK at 15K (field change 0–10kOe), 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∼111K with MTb=8.86(15)B and MCo=0.26(2)B at 2K.