Magnetic ordering in Sc2CoSi2-type R2FeSi2 (R=Gd, Tb) and R2CoSi2 (R=Y, Gd–Er) compounds

Magnetic and magnetocaloric properties of Sc2CoSi2-type R2TSi2 (R=Gd–Er, T=Fe, Co) compounds have been studied using magnetization data. These indicate the presence of mixed ferromagnetic and antiferromagnetic interactions in these compounds. One observes a ferromagnetic transition followed by an antiferromagnetic order and a further possible spin-reorientation transition at low temperatures. Compared to Gd2{Fe, Co}Si2, the Tb2FeSi2 and {Tb–Er}2CoSi2 compounds exhibit remarkable hysteresis (for e.g. Tb2FeSi2 shows residual magnetization Mres/Tb=2.45μB, coercive field Hcoer=14.9kOe, and critical field Hcrit~5kOe at 5K) possibly due to the magnetocrystalline anisotropy of the rare earth. The R2{Fe, Co}Si2 show relatively small magnetocaloric effect (i.e. isothermal magnetic entropy change, ΔSm) around the magnetic transition temperature: the maximal value of MCE is demonstrated by Ho2CoSi2 (ΔSm=−8.1J/kgK at 72K and ΔSm=−9.4J/kgK at 23K in field change of 50kOe) and Er2CoSi2 (ΔSm=−13.6J/kgK at 32K and ΔSm=−8.4J/kgK at 12K in field change of 50kOe).