Magnetic ordering of Sm26Co11Ga6-type R26Co9-6Ga8-11 compounds (R = Gd–Ho, Tm)

Abstract The magnetic ordering of polycrystalline Sm26Co11Ga6-type {Gd, Dy, Ho, Tm}26Co9Ga8 and Tb26Co6-8Ga11-9 (space group P4/mbm, N 127, tP86) has been established using magnetic measurements. Gd26Co9Ga8 exhibits soft ferromagnetic with the Curie temperature of 124 K Tb26Co6Ga11, Tb26Co8Ga9, Dy26Co9Ga8 and Ho26Co9Ga8 show mixed ferro-antiferromagnic ordering with the Curie temperatures of 76 K, 74 K, 28 K and 16 K, respectively. They display permanent magnet properties at low temperatures. The novel Tm26Co9Ga8 demonstrates dominant antiferromagnetic ordering at 6 K, while it is a soft ferromagnet at 2 K. Among these compounds, Tb26Co8Ga9 exhibits largest magnetocaloric effect with magnetic entropy change of −9.2 J/kg⋅K at 76–81 K and relative large cooling power of ~560 J/kg (field change of 50 kOe), while Tb26Co6Ga11 is the best permanent magnet with a coercivity of 9 kOe, residual magnetization of 3.26 μB per Tb and theoretical energy product of 200 kJ/m3 at 2 K.