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

• {Gd–Er}2{Fe, Co}Si2 show high-temperature ferromagnetic-type transitions.
• {Gd–Er}2{Fe, Co}Si2 show low-temperature spin-reorientation transitions.
• Tb2FeSi2 and {Tb–Er}2CoSi2 compounds exhibit low-temperature hysteresis.
• Tb2FeSi2 shows Mres/Tb=2.45 μB, Hcoer=14.9 kOe and Hcrit ~5 kOe at 5 K
• Considerable magnetocaloric effect is exhibited by Ho2CoSi2 and Er2CoSi2.

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=2.45 μB, coercive field Hcoer=14.9 kOe, and critical field Hcrit~5 kOe at 5 K) 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=−8.1 J/kg K at 72 K and ΔSm=−9.4 J/kg K at 23 K in field change of 50 kOe) and Er2CoSi2 (ΔSm=−13.6 J/kg K at 32 K and ΔSm=−8.4 J/kg K at 12 K in field change of 50 kOe).

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