Sm26Co11Ga6-type R26{Co, Ni}6.5-9.4Ga10.5-7.6 compounds (R = Gd–Er): Crystal structure, magnetic ordering and heat capacity

Abstract

The crystal structure of novel Sm26Co11Ga6-type {Gd - Er}26Ni6.5-8Ga10.5-9 compounds (space group P4/mbm, N 127, tP86) has been established using powder X-ray diffraction. The magnetic ordering and magnetocaloric effect of polycrystalline Er26Co9Ga8, Tb26Ni8Ga9 and Tb26Co9.4Ga7.6 have been investigated using magnetic and heat capacity measurements. Er26Co9Ga8 and Tb26Ni8Ga9 show mixed ferro-antiferromagnetic ordering and remarkable permanent magnet properties at low temperatures. Er26Co9Ga8 exhibits a large magnetocaloric effect with magnetic entropy change of −11.8 ​J/kg⋅K at 12 ​K and adiabatic temperature of 9.6 ​K for a field change of 50 ​kOe. The ‘Gd26Ni8Ga9’ alloy is composed of 88 ​wt% of Gd26Ni8Ga9 and 12 ​wt% of GdNi which are both soft ferromagnetic. Due to their close Curie temperatures, the composite of Gd26Ni8Ga9 and GdNi displays a table-like magnetocaloric effect with a wide temperature range from 68 ​K to 103 ​K.